Low-color scratch-resistant articles with a multilayer optical film

ABSTRACT

Embodiments of this disclosure pertain to articles that exhibit scratch-resistance and improved optical properties. In some examples, the article exhibits a color shift of about 2 or less, when viewed at an incident illumination angle in the range from about 0 degrees to about 60 degrees from normal under an illuminant. In one or more embodiments, the articles include a substrate, and an optical film disposed on the substrate. The optical film includes a scratch-resistant layer and an optical interference layer. The optical interference layer may include one or more sub-layers that exhibit different refractive indices. In one example, the optical interference layer includes a first low refractive index sub-layer and a second a second high refractive index sub-layer. In some instances, the optical interference layer may include a third sub-layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application and claims the benefit ofpriority under 35 U.S.C. § 120 of Ser. No. 15/142,508, filed Apr. 29,2016, which is a divisional application and claims the benefit ofpriority under 35 U.S.C. §120 of Ser. No. 14/480,898, filed Sep. 9,2014, which in turn claims the benefit of priority under 35 U.S.C. § 119of U.S. Provisional Application Ser. No. 62/034,412 filed on Aug. 7,2014, of U.S. Provisional Application Ser. No. 61/954,697 filed on Mar.18, 2014, and of U.S. Provisional Application Ser. No. 61/877,568 filedon Sep. 13, 2013, the contents of which are relied upon and incorporatedherein by reference in their entirety. Application Ser. No. 15/142,508filed on Apr. 29, 2016 is a continuation-in-part application and claimsthe benefit of priority under 35 U.S.C. § 120 of U.S. application Ser.No. 14/331,656 filed Jul. 15, 2014, which is a continuation and claimsthe benefit of priority under 35 U.S.C. § 120 of U.S. application Ser.No. 14/262,066 filed on Apr. 25, 2014, which in turns claims the benefitof priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser.No. 61/954,697 filed on Mar. 18, 2014, of U.S. Provisional ApplicationSer. No. 61/877,568 filed on Sep. 13, 2013, and of U.S. ProvisionalApplication Ser. No. 61/820,407 filed on May 7, 2013, the contents ofwhich are relied upon and incorporated herein by reference in theirentirety.

BACKGROUND

The disclosure relates to articles with scratch resistance, abrasionresistance or a combination thereof, which also exhibit retained opticalproperties and more particularly to articles that exhibit a highhardness and low color shift when viewed at different incidentillumination angles.

Cover and housing substrates are often used in consumer electronicproducts to protect critical devices within the product, to provide auser interface for input and/or display, and/or many other functions.Such consumer electronic products include mobile devices, such as smartphones, mp3 players and computer tablets. Cover and housing substratesmay also be used in architectural articles, transportation-relatedarticles, appliance articles, or any article that requires sometransparency, scratch-resistance, abrasion resistance or a combinationthereof. These applications and others also often demand durable (e.g.,scratch-resistant) cover and housing substrate, which also has strongoptical performance characteristics. Often, the cover substrate includesglass for this purpose; however other substrates may be used.

Strong optical performance in terms of maximum light transmission andminimum reflectivity are required in cover substrate applications (andpotentially in some housing substrate applications). Furthermore, coversubstrate applications require that the color exhibited or perceived, inreflection and/or transmission, does not change appreciably as theviewing angle (or incident illumination angle) is changed. This isbecause, if the color, reflectivity or transmission changes with viewingangle to an appreciable degree, the user of the product incorporatingthe cover glass will perceive a change in the color or brightness of thedisplay, which can diminish the perceived quality of the display. Ofthese changes, a change in color is often the most noticeable andobjectionable to users.

Known cover substrates include glass and film combinations can oftenexhibit a variety of different types of scratches after use in harshoperating conditions. In some instances, a significant portion of thosescratches are microductile scratches, which typically include a singlegroove in a material having extended length and with depths in the rangefrom about 100 nm to about 500 nm. Microductile scratches may beaccompanied by other types of visible damage, such as sub-surfacecracking, frictive cracking, chipping and/or wear. Evidence suggeststhat a majority of such scratches and other visible damage is caused bysharp contact that occurs in a single contact event. Once a significantscratch appears on the cover substrate, the appearance of the product isdegraded since the scratch causes an increase in light scattering, whichmay cause significant reduction in brightness, clarity and contrast ofimages on the display. Significant scratches can also affect theaccuracy and reliability of touch sensitive displays. A portion of suchscratches and other visible damage as described above may also be causedby multiple contact events (including reciprocating abrasion or wear).These scratches, and even less significant scratches, are unsightly andcan affect product performance.

Single event scratch damage can be contrasted with abrasion damage.Abrasion damage is typically caused by multiple contact events, such asreciprocating sliding contact from hard counter face objects (e.g.,sand, gravel and sandpaper). Abrasion damage can generate heat, whichcan degrade chemical bonds in the film materials and cause flaking andother types of damage to the cover glass. In addition, since abrasiondamage is often experienced over a longer term than the single eventsthat cause scratches, the film material experiencing abrasion damage canalso oxidize, which further degrades the durability of the film and thusthe glass-film laminate. The single events that cause scratchesgenerally do not involve the same conditions as the events that causeabrasion damage and therefore, the solutions often utilized to preventabrasion damage may not also prevent scratches in cover substrates.Moreover, known scratch and abrasion damage solutions often compromisethe optical properties.

Accordingly, there is a need for new cover substrates, and methods fortheir manufacture, which are scratch resistant over a wide range ofdifferent types of scratches, abrasion resistant, and have good opticalperformance.

SUMMARY

One aspect of the present disclosure pertains to an article including asubstrate with a surface and an optical film disposed on the surface ofthe substrate forming a coated surface. The article of one or moreembodiments exhibits a transmittance color and/or reflectance such thatthe transmittance color coordinates and/or the reflectance colorcoordinates (measured at the coated surface) have color shift of about 2or less or a color shift of about 0.5 or less, when viewed at anincident illumination angle in the range from about 0 degrees to about60 degrees from normal incidence under an illuminant. Exemplaryilluminants include International Commission on Illumination (“CIE”) F2or CIE F10.

The article of some embodiments may exhibit a hardness of about 8 GPa orgreater, as measured by a Berkovich Indenter Hardness Test, as describedherein, along an indentation depth of about 100 nm or greater (e.g.,from about 100 nm to about 300 nm, from about 100 nm to about 400 nm,from about 100 nm to about 500 nm, or from about 100 nm to about 600nm). The article may optionally include a crack mitigating layerdisposed between the optical film and the substrate or within theoptical film.

In one or more embodiments, the optical film includes ascratch-resistant layer. The scratch-resistant layer may exhibit ahardness of about 8 GPa or greater, as measured by the BerkovichIndenter Hardness Test. The scratch-resistant layer of some embodimentsmay exhibit a refractive index of about 1.7 or greater. Thescratch-resistant layer may include one or more of AlN, Si₃N₄,AlO_(x)N_(y), SiO_(x)N_(y), Al₂O₃, Si_(x)C_(y), Si_(x)O_(y)C_(z), ZrO₂,TiO_(x)N_(y), diamond, diamond-like carbon, and Si_(u)Al_(v)O_(x)N_(y).

The optical film of one or more embodiments includes an opticalinterference layer disposed between the scratch-resistant layer and thesubstrate. The optical interference layer may include a first lowrefractive index (RI) sub-layer and a second high RI sub-layer. Thedifference between the refractive index of the first low RI sub-layerand the refractive index of the second high RI sub-layer may be about0.01 or greater (e.g., about 0.1 or greater, about 0.2 or greater, about0.3 or greater or about 0.4 or greater). In one or more embodiments, theoptical interference layer includes a plurality of sub-layer sets (e.g.,up to about 10 sub-layer sets), which can include a first low RIsub-layer and a second high RI sub-layer. The first low RI sub-layer mayinclude one or more of SiO₂, Al₂O₃, GeO₂, SiO, AlO_(x)N_(y),SiO_(x)N_(y), Si_(n)Al_(v)O_(x)N_(y), MgO, MgF₂, BaF₂, CaF₂, DyF₃, YbF₃,YF₃, and CeF₃. The second high RI rub-layer may include at least one ofSi_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, AlN, Si₃N₄, AlO_(x)N_(y),SiO_(x)N_(y), HfO₂, TiO₂, ZrO₂, Y₂O₃, Al₂O₃, and MoO₃.

In some instances, the optical interference layer includes a thirdsub-layer. The third sub-layer may be disposed between the plurality ofsub-layer sets and the scratch-resistant layer. Alternatively, the thirdsub-layer may be disposed between the substrate and the plurality ofsub-layer sets. The third sub-layer of one or more embodiments may havea RI between the refractive index of the first low RI sub-layer and therefractive index of the second high RI sub-layer. The optical film ofsome embodiments may include a capping layer disposed on thescratch-resistant layer.

The first low RI sub-layer and/or the second high RI sub-layer of theoptical interference layer may have an optical thickness (n*d) in therange from about 2 nm to about 200 nm. The optical interference layermay exhibit a thickness of about 800 nm or less.

In some embodiments, the optical interference layer exhibits an averagelight reflection of about 0.5% or less over the optical wavelengthregime. In some embodiments, the article exhibits an averagetransmittance or average reflectance having an average oscillationamplitude of about 5 percentage points or less over the opticalwavelength regime.

The substrate of one or more embodiments may include an amorphoussubstrate or a crystalline substrate. The amorphous substrate caninclude a glass selected from the group consisting of soda lime glass,alkali aluminosilicate glass, alkali containing borosilicate glass andalkali aluminoborosilicate glass. The glass may be optionally chemicallystrengthened and/or may include a compressive stress (CS) layer with asurface CS of at least 250 MPa extending within the chemicallystrengthened glass from a surface of the chemically strengthened glassto a depth of layer (DOL). The DOL exhibited by such substrates may beat least about 10 μm.

The articles disclosed herein may include articles with a display (ordisplay articles) (e.g., consumer electronics, including mobile phones,tablets, computers, navigation systems, and the like), architecturalarticles, transportation articles (e.g., automotive, trains, aircraft,sea craft, etc.), appliance articles, or any article that requires sometransparency, scratch-resistance, abrasion resistance or a combinationthereof.

Additional features and advantages will be set forth in the detaileddescription which follows. Additional features and advantages will bereadily apparent to those skilled in the art from that description orrecognized by practicing the embodiments described herein and in theappended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description, serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a known substrate and a scratch-resistantmaterial embodiment;

FIG. 2 is an illustration of a known article including a single layerinterference layer;

FIG. 3 is a reflectance spectra for the article shown in FIG. 2;

FIG. 4 is a graph showing the range of calculated a* and b* color shiftsbased on the reflectance spectra shown in FIG. 3;

FIG. 5 is illustration of an article according to one or moreembodiments;

FIG. 6 is a more detailed illustration of the article shown in FIG. 5;

FIG. 7 is a calculated reflectance spectra for the article having anoptical interference layer with three sub-layer sets, according tomodeled Example 1;

FIG. 8 is a graph showing the range of calculated a* and b* color shiftsfor modeled Example 1;

FIG. 9 is a schematic representation of the article according to modeledExample 2;

FIG. 10 is a calculated reflectance spectra for the article according tomodeled Example 2;

FIG. 11 is a graph showing the range of calculated a* and b* colorshifts for modeled Example 2;

FIG. 12 is a schematic representation of the article according tomodeled Example 3;

FIG. 13 is a calculated reflectance spectra for the article according tomodeled Example 3;

FIG. 14 is a graph showing the range of calculated a* and b* colorshifts for modeled Example 3;

FIG. 15 is a schematic representation of the article according tomodeled Example 4;

FIG. 16 is a calculated reflectance spectra for the article according tomodeled Example 4;

FIG. 17 is a graph showing the range of calculated a* and b* colorshifts for modeled Example 4;

FIG. 18 is a schematic representation of the article according tomodeled Example 5;

FIG. 19 is a calculated reflectance spectra for the article according tomodeled Example 5;

FIG. 20 is a schematic representation of the article according tomodeled Example 6;

FIG. 21 is a calculated reflectance spectra for the article according tomodeled Example 6;

FIG. 22 is a schematic representation of the article according tomodeled Example 7;

FIG. 23 is a calculated reflectance spectra for the article according tomodeled Example 7;

FIG. 24 is a schematic representation of the article according tomodeled Example 8;

FIG. 25 is a calculated reflectance spectra for the article according tomodeled Example 8;

FIG. 26 is a graph showing the range of calculated a* and b* colorshifts for modeled Examples 6-8;

FIG. 27 is a schematic representation of the article according tomodeled Example 9;

FIG. 28 is a calculated reflectance spectra for the article according tomodeled Example 9;

FIG. 29 shows the measured transmittance spectra for articles accordingto Examples 10-11 and Comparative Example 12;

FIG. 30 shows the measured reflected color coordinates for Examples10-11 and bare glass at different incident illumination angles;

FIG. 31 shows the measured transmitted light color coordinates forExamples 10-11 at an incident illumination angle of 5 degrees; and

FIG. 32 is a schematic representation of the article according tomodeled Example 13.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiment(s), examplesof which are illustrated in the accompanying drawings. Wheneverpossible, the same reference numerals will be used throughout thedrawings to refer to the same or like parts.

Known scratch-resistant materials, such as AlN, Si₃N₄, AlO_(x)N_(y), andSiO_(x)N_(y), have high refractive indices, for example, in the rangefrom about 1.7 to about 2.1. Common substrates that includescratch-resistant materials are glass and plastic substrates. Glass andplastic materials typically have refractive indices in the range fromabout 1.45 to about 1.65. This difference in the refractive index of thescratch-resistant materials and the substrate can contribute toundesirable optical interference effects. These undesirable opticalinterference effects may be more pronounced where the scratch-resistantmaterials have a physical thickness in the range from about 0.05 toabout 10 microns. Optical interference between reflected waves from thescratch-resistant material/air interface 10 (as shown in FIG. 1) and thescratch-resistant material/substrate interface 20 (as shown in FIG. 1)can lead to spectral reflectance oscillations that create apparent colorin the scratch-resistant materials 30 (and/or the combination of thescratch-resistant materials 30 and substrate 40), particularly inreflection. The color shifts in reflection with viewing angle due to ashift in the spectral reflectance oscillations with incidentillumination angle. The observed color and color shifts with incidentillumination angle are often distracting or objectionable to deviceusers, particularly under illumination with sharp spectral features suchas fluorescent lighting and some LED lighting.

Observed color and color shifts can be reduced by minimizing thereflectance at one or both interfaces 10, 20, thus reducing reflectanceoscillations and reflected color shifts for the entire article. Forscratch-resistant materials, the reduction in reflectance is often mostfeasible at the scratch-material/substrate interface 20, whilesimultaneously retaining the high durability or scratch resistance ofthe scratch-resistant materials/air interface 10. Various ways to reducereflectance include the use of a single optical interference layer (asshown in FIG. 2) or a layer having a monotonic gradient in refractiveindex at the scratch-resistant material/substrate interface 20. Suchoptions, however, often exhibit large oscillations in the transmittanceand/or reflectance spectra under various illuminants. A single layerinterference layer is included in the article shown in FIG. 2. Thearticle includes an alkali aluminoborosilicate glass substrate 10, asingle layer interference layer 50 of Al₂O₃ having a physical thicknessof about 80 nanometers (nm), an scratch-resistant layer 30 ofSi_(u)Al_(v)O_(x)N_(y) having a physical thickness of about 2000 nm, anda layer 60 of SiO₂ having a physical thickness of about 10 nm. FIG. 3shows a modeled reflectance spectrum for the article illustrated in FIG.2. The spectrum exhibits oscillations over the optical wavelength regimehaving amplitudes in the range from about 3.5 percentage points (e.g., alow reflectance of about 8.5% and a peak reflectance of about 12%, atthe wavelength range from about 520 nm to 540 nm) to about 8 percentagepoints (e.g., a low reflectance of about 6.5% and a peak reflectance toabout 14.5%, at the wavelength of about 400 nm to 410 nm). As usedherein, the term “amplitude” includes the peak-to-valley change inreflectance or transmittance. As used herein, the term “transmittance”is defined as the percentage of incident optical power within a givenwavelength range transmitted through a material (e.g., the article, thesubstrate or the optical film or portions thereof). The term“reflectance” is similarly defined as the percentage of incident opticalpower within a given wavelength range that is reflected from a material(e.g., the article, the substrate, or the optical film or portionsthereof). Transmittance and reflectance are measured using a specificlinewidth. In one or more embodiments, the spectral resolution of thecharacterization of the transmittance and reflectance is less than 5 nmor 0.02 eV.

The phrase “average amplitude” includes the peak-to-valley change inreflectance or transmittance averaged over every possible 100 nmwavelength range within the optical wavelength regime. As used herein,the “optical wavelength regime” includes the wavelength range from about420 nm to about 700 nm. From this information, it can be predicted thatthe article shown in FIGS. 2 and 3 will exhibit relatively large colorshifts when viewed at different incident illumination angles from normalincidence under different illuminants, as shown in FIG. 4.

The embodiments of this disclosure utilize an optical interference layerincluding multiple layers disposed between the substrate and thescratch-resistant materials. The optical interference layer achievesimproved optical performance, in terms of colorlessness and/or smallercolor shifts with viewed at varying incident illumination angles fromnormal incidence under different illuminants. Such optical interferencelayers are amenable to faster manufacturing over monotonic gradientdesigns, and articles incorporating optical interference layers providescratch-resistance and superior optical properties.

A first aspect of this disclosure pertains to an article that exhibitscolorlessness even when viewed at different incident illumination anglesunder an illuminant. In one or more embodiments, the article exhibits acolor shift of about 2 or less for any incidental illumination angles inthe ranges provided herein. As used herein, the phrase “color shift”refers to the change in both a* and b* values, under the CIE L*, a*, b*colorimetry system, in reflectance or transmittance. The a* and b*values are described as transmittance color (or transmittance colorcoordinates) or reflectance color (or reflectance color coordinates),respectively. Color shift may be determined using the followingequation: √((a*₂−a*₁)²+(b*₂−b*₁)²), a* and b* coordinates (intransmittance or reflectance) of the article when viewed at normalincidence (i.e., a*₁, and b*₁) and at an incident illumination angleaway from normal incidence (i.e., a*₂, and b*₂), provided that theincident illumination angle is different from normal incidence and insome cases differs from normal incidence by at least about 2 degrees orabout 5 degrees. Measurements of the various colors over a collection ofdifferent observers indicates that the average observer sees ajust-noticeable difference in the two colors when the color shift is ofabout 2.

In some instances, a color shift of about 2 or less is exhibited by thearticle when viewed at various incident illumination angles from normalincidence, under an illuminant. In some instances the color shift isabout 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less,1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, 0.9 orless, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less,0.3 or less, 0.2 or less, or 0.1 or less. In some embodiments, the colorshift may be about 0. The illuminant can include standard illuminants asdetermined by the CIE, including A illuminants (representingtungsten-filament lighting), B illuminants (representing daylightsimulating illuminants), C illuminants (representing daylight simulatingilluminants), D series illuminants (representing natural daylight), andF series illuminants (representing various types of fluorescentlighting). In specific examples, the articles exhibit a color shift ofabout 2 or less when viewed at incident illumination angle from normalincidence under a CIE F2, F10, F11, F12 or D65 illuminant. The incidentillumination angle may be in the range from about 0 degrees to about 80degrees, from about 0 degrees to about 75 degrees, from about 0 degreesto about 70 degrees, from about 0 degrees to about 65 degrees, fromabout 0 degrees to about 60 degrees, from about 0 degrees to about 55degrees, from about 0 degrees to about 50 degrees, from about 0 degreesto about 45 degrees, from about 0 degrees to about 40 degrees, fromabout 0 degrees to about 35 degrees, from about 0 degrees to about 30degrees, from about 0 degrees to about 25 degrees, from about 0 degreesto about 20 degrees, from about 0 degrees to about 15 degrees, fromabout 5 degrees to about 80 degrees, from about 5 degrees to about 80degrees, from about 5 degrees to about 70 degrees, from about 5 degreesto about 65 degrees, from about 5 degrees to about 60 degrees, fromabout 5 degrees to about 55 degrees, from about 5 degrees to about 50degrees, from about 5 degrees to about 45 degrees, from about 5 degreesto about 40 degrees, from about 5 degrees to about 35 degrees, fromabout 5 degrees to about 30 degrees, from about 5 degrees to about 25degrees, from about 5 degrees to about 20 degrees, from about 5 degreesto about 15 degrees, and all ranges and sub-ranges therebetween, awayfrom normal incidence. The article may exhibit the maximum color shiftsdescribed herein at and along all the incident illumination angles inthe range from about 0 degrees to about 80 degrees away from normalincidence. In one example, the article may exhibit a color shift of 2 orless at any incident illumination angle in the range from about 0degrees to about 60 degrees, from about 2 degrees to about 60 degrees,or from about 5 degrees to about 60 degrees away from normal incidence.

According to one or more embodiments, the article 100 exhibits anaverage transmittance of 85% or greater over the visible spectrum. Inone or more embodiments, the article 100 has a total reflectance of 15%or less.

Referring to FIG. 5, the article 100 according to one or moreembodiments may include a substrate 110, and an optical film 120disposed on the substrate. The substrate 110 includes opposing majorsurfaces 112, 114 and opposing minor surfaces 116, 118. The optical film120 is shown in FIG. 5 as being disposed on a first opposing majorsurface 112; however, the optical film 120 may be disposed on the secondopposing major surface 114 and/or one or both of the opposing minorsurfaces, in addition to or instead of being disposed on the firstopposing major surface 112. The article 100 includes a coated surface101.

The optical film 120 includes at least one layer of at least onematerial. The term “layer” may include a single layer or may include oneor more sub-layers. Such sub-layers may be in direct contact with oneanother. The sub-layers may be formed from the same material or two ormore different materials. In one or more alternative embodiments, suchsub-layers may have intervening layers of different materials disposedtherebetween. In one or more embodiments a layer may include one or morecontiguous and uninterrupted layers and/or one or more discontinuous andinterrupted layers (i.e., a layer having different materials formedadjacent to one another). A layer or sub-layers may be formed by anyknown method in the art, including discrete deposition or continuousdeposition processes. In one or more embodiments, the layer may beformed using only continuous deposition processes, or, alternatively,only discrete deposition processes.

As used herein, the term “dispose” includes coating, depositing and/orforming a material onto a surface using any known method in the art. Thedisposed material may constitute a layer, as defined herein. The phrase“disposed on” includes the instance of forming a material onto a surfacesuch that the material is in direct contact with the surface and alsoincludes the instance where the material is formed on a surface, withone or more intervening material(s) is between the disposed material andthe surface. The intervening material(s) may constitute a layer, asdefined herein.

The articles described herein have scratch resistance, which may becharacterized by a measured hardness of the article (or the measuredhardness of the optical film, which may include a scratch resistantlayer, as described herein). Hardness may be measured by a “BerkovichIndenter Hardness Test”, which includes measuring the hardness of amaterial on a surface thereof by indenting the surface with a diamondBerkovich indenter. The Berkovich Indenter Hardness Test includesindenting the coated surface 101 of the article or the surface of theoptical film (which may include the scratch resistant layer, describedherein) with the diamond Berkovich indenter to form an indent to anindentation depth in the range from about 50 nm to about 1000 nm (or theentire thickness of the optical film, whichever is less) and measuringthe maximum hardness from this indentation along the entire indentationdepth range or a segment of this indentation depth (e.g., in the rangefrom about 100 nm to about 600 nm), generally using the methods setforth in Oliver, W. C.; Pharr, G. M. An improved technique fordetermining hardness and elastic modulus using load and displacementsensing indentation experiments. J. Mater. Res., Vol. 7, No. 6, 1992,1564-1583; and Oliver, W. C.; Pharr, G. M. Measurement of Hardness andElastic Modulus by Instrument Indentation: Advances in Understanding andRefinements to Methodology. J. Mater. Res., Vol. 19, No. 1, 2004, 3-20.The indentation depth is made and measured from the coated surface 101of the article, the surface of the optical film and/or surface of anyone or more of the layers in the optical film. As used herein, hardnessrefers to a maximum hardness, and not an average hardness.

Typically in nanoindentation measurement methods (such as by using aBerkovich indenter) of a coating or film that is harder than theunderlying substrate, the measured hardness may appear to increaseinitially due to development of the plastic zone at shallow indentationdepths and then increases and reaches a maximum value or plateau atdeeper indentation depths. Thereafter, hardness begins to decrease ateven deeper indentation depths due to the effect of the underlyingsubstrate. Where a substrate having an increased hardness compared tothe coating is utilized, the same effect can be seen; however, thehardness increases at deeper indentation depths due to the effect of theunderlying substrate.

The indentation depth range and the hardness values at certainindentation depth range(s) can be selected to identify a particularhardness response of the optical film and layers thereof, describedherein, without the effect of the underlying substrate. When measuringhardness of the optical film or layers thereof (when disposed on asubstrate) with a Berkovich indenter, the region of permanentdeformation (plastic zone) of a material is associated with the hardnessof the material. During indentation, an elastic stress field extendswell beyond this region of permanent deformation. As indentation depthincreases, the apparent hardness and modulus are influenced by stressfield interactions with the underlying substrate. The substrateinfluence on hardness occurs at deeper indentation depths (i.e.,typically at depths greater than about 10% of the optical film structureor layer thickness). Moreover, a further complication is that thehardness response requires a certain minimum load to develop fullplasticity during the indentation process. Prior to that certain minimumload, the hardness shows a generally increasing trend.

At small indentation depths (which also may be characterized as smallloads) (e.g., up to about 100 nm, or less than about 70 nm), theapparent hardness of a material appears to increase dramatically versusindentation depth. This small indentation depth regime does notrepresent a true metric of hardness but instead, reflects thedevelopment of the aforementioned plastic zone, which is related to thefinite radius of curvature of the indenter. At intermediate indentationdepths, the apparent hardness approaches maximum levels. At deeperindentation depths, the influence of the substrate becomes morepronounced as the indentation depths increase. Hardness may begin todrop dramatically once the indentation depth exceeds about 30% of theoptical film structure thickness or the layer thickness.

It has been observed that the hardness measured at intermediateindentation depths (at which hardness approaches and is maintained atmaximum levels) and at deeper indentation depths depends on thethickness of a material or layer. Specifically, the hardness response offour different layers (i.e., 500 nm thick, 1000 nm thick, 1500 nm thick,and 2000 nm thick) of AlO_(x)N_(y) having different thicknesses wasevaluated. The hardness of each layer was measured using the BerkovichIndenter Hardness Test. The 500 nm-thick layer exhibited its maximumhardness at indentation depths from about 100 nm to 180 nm, followed bya dramatic decrease in hardness at indentation depths from about 180 nmto about 200 nm, indicating the hardness of the substrate influencingthe hardness measurement. The 1000 nm-thick layer exhibited a maximumhardness at indentation depths from about 100 nm to about 300 nm,followed by a dramatic decrease in hardness at indentation depthsgreater than about 300 nm. The 1500 nm-thick layer exhibited a maximumhardness at indentation depths from about 100 nm to about 550 nm and the2000-nm thick layer exhibited a maximum hardness at indentation depthsfrom about 100 nm to about 600 nm.

In some embodiments, the article, the optical film and/or layer(s) inthe optical film exhibit a maximum hardness at indentation depthsgreater than about 100 nm or greater than about 200 nm and thus exhibitsufficient hardness to provide scratch resistance, that is notinfluenced by the substrate. In some embodiments, the article, theoptical film and/or layer(s) in the optical film have a maximum hardnessat such indentation depths and thus are resistant to specific scratchessuch as microductile scratches (which typically have depths of about 100nm to about 500 nm or from about 200 nm to about 400 nm). For example,the coated surface 101 (or the surface of the optical film or any one ormore layers of the optical film) may be resistant to microductilescratches because the article exhibits the hardness values recitedherein along specific indentation depths, as measured by a BerkovichIndenter Hardness Test.

The measured or apparent hardness of the article and/or optical film (orlayers in the optical film) may be maximized by tuning the thickness ofthe optical film or one or more layer(s) in the optical film.

In one or more embodiments, the article 100 exhibits an average hardnessof about 8 GPa or greater, about 10 GPa or greater, about 14 GPa orgreater, about 18 GPa or greater, as measured by the Berkovich IndenterHardness test. In some embodiments, the average hardness of the articlemay be in the range from about 5 GPa to about 30 GPa, from about 6 GPato about 30 GPa, from about 7 GPa to about 30 GPa, from about 8 GPa toabout 30 GPa, from about 9 GPa to about 30 GPa, from about 10 GPa toabout 30 GPa, from about 12 GPa to about 30 GPa, from about 5 GPa toabout 28 GPa, from about 5 GPa to about 26 GPa, from about 5 GPa toabout 24 GPa, from about 5 GPa to about 22 GPa, from about 5 GPa toabout 20 GPa, from about 12 GPa to about 25 GPa, from about 15 GPa toabout 25 GPa, from about 16 GPa to about 24 GPa, from about 18 GPa toabout 22 GPa and all ranges and sub-ranges therebetween. These hardnessvalues may be present at indentation depths of about 50 nm or greater,or about 100 nm or greater (e.g., (e.g., from about 100 nm to about 300nm, from about 100 nm to about 400 nm, from about 100 nm to about 500nm, from about 100 nm to about 600 nm, from about 200 nm to about 300nm, from about 200 nm to about 400 nm, from about 200 nm to about 500nm, or from about 200 nm to about 600 nm).

In one or more embodiments, article 100 also exhibits abrasionresistance. Specifically, one or more embodiments of the articlesdescribed herein exhibit resistance to scratches and other damage formedby abrasion (or multiple contact events). Various forms of abrasion testare known in the art, such as that specified in ASTM D1044-99, usingabrasive media supplied by Taber Industries. Modified abrasion methodsrelated to ASTM D1044-99 can be created using different types ofabrading media, abradant geometry and motion, pressure, etc. in order toprovide repeatable and measurable abrasion or wear tracks tomeaningfully differentiate the abrasion resistance of different samples.For example, different test conditions will usually be appropriate forsoft plastics vs. hard inorganic test samples. The embodiments describedherein exhibit scratch resistance as measured by a specific modifiedversion of the ASTM D1044-99 test referred to herein as the “TaberTest”, or a “Garnet Test”, which provide clear and repeatabledifferentiation of durability between different samples, which compriseprimarily hard inorganic materials. These test methods may generate acombination of micro-ductile scratches together with other damage modesmentioned above, depending on the specific sample tested.

As used herein, the phrase “Taber Test” refers to a test method using aTaber Linear Abraser 5750 (TLA 5750) and accessories supplied by TaberIndustries, in an environment including a temperature of about 22° C.±3°C. and Relative Humidity of up to about 70%. The TLA 5750 includes aCS-17 abraser material having a 6.7 mm diameter abraser head. Eachsample was abraded according to the Taber Test and the abrasive damagewas evaluated using both Haze and Bidirectional TransmittanceDistribution Function (BTDF) measurements, among other methods. In theTaber Test, the procedure for abrading each sample includes placing theTLA 5750 and a flat sample support on a rigid, flat surface and securingthe TLA 5750 and the sample support to the surface. Before each sampleis abraded under the Taber Test, the abraser material (CS-17) is refacedusing a new S-14 refacing strip adhered to glass. The abraser issubjected to 10 refacing cycles using a cycle speed of 25 cycles/minuteand stroke length of 1 inch, with no additional weight added (i.e., atotal weight of about 350 g is used during refacing, which is thecombined weight of the spindle and collet holding the abraser). Theprocedure then includes operating the TLA 5750 to abrade the sample,where the sample is placed in the sample support in contact with theabraser head and supporting the weight applied to the abraser head,using a cycle speed of 25 cycles/minute, and a stroke length of 1 inch,and a weight such that the total weight applied to the sample is 850 g(i.e., a 500 g auxiliary weight is applied in addition to the 350 gcombined weight of the spindle and collet). The procedure includesforming two wear tracks on each sample for repeatability, and abradingeach sample for 500 cycle counts in each of the two wear tracks on eachsample.

In one or more embodiments, the coated surface 101 of the article isabraded according to the above Taber Test and the article exhibits ahaze of about 5% or less, as measured on the abraded side using ahazemeter supplied by BYK Gardner under the trademark Haze-Gard plus®,using an aperture over the source port, the aperture having a diameterof 8 mm.

In some embodiments, the haze measured after the Taber Test may be about4% or less, about 3% or less, about 2% or less, about 1% or less, about0.8% or less, about 0.5% or less, about 0.4% or less, about 0.3%, about0.2% or less, or about 0.1% or less.

In one or more embodiments, the coated surface 101 of the article mayexhibit an abrasion resistance, after being abraded by the Taber Test asmeasured by a light scattering measurement. In one or more embodiments,the light scattering measurement includes a bi-directional reflectancedistribution function (BRDF) or bi-directional transmittancedistribution function (BTDF) measurement carried out using a RadiantZemax IS-SA™ instrument. This instrument has the flexibility to measurelight scattering using any input angle from normal to about 85 degreesincidence in reflection, and from normal to about 85 degrees incidencein transmission, while also capturing all scattered light output ineither reflection or transmission into 2*Pi steradians (a fullhemisphere in reflection or transmission). In one embodiment, thearticle 100 exhibits an abrasion resistance, as measured using BTDF atnormal incidence and analyzing the transmitted scattered light at aselected angular range, for example from about 10° to about 80° degreesin polar angles and any angular range therein. The full azimuthal rangeof angles can be analyzed and integrated, or particular azimuthalangular slices can be selected, for example from about 0° and 90°azimuthally. In the case of linear abrasion an azimuthal direction thatis substantially orthogonal to the abrasion direction may be utilized soas to increase signal-to-noise of the optical scattering measurement. Inone or more embodiments, the article may exhibit a scattered lightintensity after the Taber Test as measured at the coated surface 101, ofabout less than about 0.1, about 0.05 or less, about 0.03 or less, about0.02 or less, about 0.01 or less, about 0.005 or less, or about 0.003 orless (in units of 1/steradian), when using the Radiant Zemax IS-SA toolin CCBTDF mode at normal incidence in transmission, with a 2 mm apertureand a monochrometer set to 600 nm wavelength, and when evaluated atpolar scattering angles in the range from about 15° to about 60° (e.g.specifically, about 20°). Normal incidence in transmission may beotherwise known as zero degrees in transmission, which may be denoted as180° incidence by the instrument software. In one or more embodiments,the scattered light intensity may be measured along an azimuthaldirection substantially orthogonal to the abraded direction of a sampleabraded by the Taber Test. These optical intensity values may alsocorrespond to less than about 1%, less than about 0.5%, less than about0.2%, or less than about 0.1% of the input light intensity that isscattered into polar scattering angles greater than about 5 degrees,greater than about 10 degrees, greater than about 30 degrees, or greaterthan about 45 degrees.

Generally speaking, BTDF testing at normal incidence, as describedherein, is closely related to the transmission haze measurement, in thatboth are measuring the amount of light that is scattered in transmissionthrough a sample (or, in this case the article, after abrading thecoated surface 101). BTDF measurements provide more sensitivity as wellas more detailed angular information, compared to haze measurements.BTDF allows measurement of scattering into different polar and azimuthalangles, for example allowing us to selectively evaluate the scatteringinto azimuthal angles that are substantially orthogonal to the abrasiondirection in the linear Taber test (these are the angles where lightscattering from linear abrasion is the highest). Transmission haze isessentially the integration of all scattered light measured by normalincidence BTDF into the entire hemisphere of polar angles greater thanabout +/−2.5 degrees.

The Garnet Test uses the same apparatus as the Taber Test (i.e., a Taberlinear abraser, or an equivalent apparatus). The Garnet Test includesusing a 150-grit garnet sandpaper to abrade the sample surface undervarying applied loads for one reciprocation cycle (i.e., oneforward-and-back cycle), with a stroke length of 1″ and a speed of 45cycles/minute. The loads applied are in terms of a total load (includingthe weight of the abraser spindle, holder, and any added weights). Thegarnet sandpaper has a contact area with the samples of about 7 mm,similar to the Taber test. The Garnet Test performed in this way isgenerally more aggressive than the Taber Test and can produce a widervariety of damage modes. The visible scratches and damage are also morerandom. Light scattering from these samples can be characterized usingBTDF and Haze measurements as described above.

In one or more embodiments, the article exhibits a haze of about 3% orless (e.g., about 2% or less, about 1% or less, about 0.5% or less, orabout 0.2% or less) after the Garnet Test, when tested in the GarnetTest with a total load in the range from about 380 g to about 2100 g.The articles of one or more embodiment exhibit a scattered light levelat a polar angle of 20 degrees (orthogonal to abrasion axis, as measuredby CC-BTDF) of about 0.04 or less, about 0.02 or less, about 0.01 orless, or even about 0.005 or less, in units of 1/steradian.

According to one or more embodiments, the article 100 exhibits anaverage light transmission of about 80% or greater. The term “lighttransmission” refers to the amount of light that is transmitted througha medium. The measure of light transmission is the difference betweenthe amount of light that enters the medium and the amount of light thatexits the medium. In other words, light transmission is the light thathas traveled through a medium without being absorbed or scattered. Theterm “average light transmission” refers to spectral average of thelight transmission multiplied by the luminous efficiency function, asdescribed by CIE standard observer. The article 100 of specificembodiments may exhibit an average light transmission of 80% or greater,82% or greater, 85% or greater, 90% or greater, 90.5% or greater, 91% orgreater, 91.5% or greater, 92% or greater, 92.5% or greater, 93% orgreater, 93.5% or greater, 94% or greater, 94.5% or greater, or 95% orgreater.

In one or more embodiments, the article 100 has a total reflectivitythat 20% or less. For example, the article may have a total reflectivityof 20% or less, 15%, or less, 10% or less, 9% or less, 8% or less, 7% orless, 6% or less. In some specific embodiments, the article has a totalreflectivity of 6.9% or less, 6.8% or less, 6.7% or less, 6.6% or less,6.5% or less, 6.4% or less, 6.3% or less, 6.2% or less, 6.1% or less,6.0% or less, 5.9% or less, 5.8% or less, 5.7% or less, 5.6% or less, or5.5% or less. In accordance with one or more embodiments, the article100 has a total reflectivity that is the same or less than the totalreflectivity of the substrate 110. In one or more embodiments, thearticle 100 exhibits a relatively flat transmittance spectrum,reflectance spectrum or transmittance and reflectance spectrum over theoptical wavelength regime. In some embodiments, the relatively flattransmittance and/or reflectance spectrum includes an averageoscillation amplitude of about 5 percentage points or less along theentire optical wavelength regime or wavelength range segments in theoptical wavelength regime. Wavelength range segments may be about 50 nm,about 100 nm, about 200 nm or about 300 nm. In some embodiments, theaverage oscillation amplitude may be about 4.5 percentage points orless, about 4 percentage points or less, about 3.5 percentage points orless, about 3 percentage points or less, about 2.5 percentage points orless, about 2 percentage points or less, about 1.75 percentage points orless, about 1.5 percentage points or less, about 1.25 percentage pointsor less, about 1 percentage point or less, about 0.75 percentage pointsor less, about 0.5 percentage points of less, about 0.25 percentagepoints or less, or about 0 percentage points, and all ranges andsub-ranges therebetween. In one or more specific embodiments, thearticle exhibits a transmittance over a selected wavelength rangesegment of about 100 nm or 200 nm over the optical wavelength regime,wherein the oscillations from the spectra have a maximum peak of about80%, about 82%, about 84%, about 86%, about 87%, about 88%, about 89%,about 90%, about 91%, about 92%, about 93%, about 94%, or about 95%, andall ranges and sub-ranges therebetween.

In some embodiments, the relatively flat average transmittance and/oraverage reflectance includes maximum oscillation amplitude, expressed asa percent of the average transmittance or average reflectance, along aspecified wavelength range segment in the optical wavelength regime. Theaverage transmittance or average reflectance would also be measuredalong the same specified wavelength range segment in the opticalwavelength regime. The wavelength range segment may be about 50 nm,about 100 nm or about 200 nm. In one or more embodiments, the article100 exhibits an average transmittance and/or average reflectance with anaverage oscillation amplitude of about 10% or less, about 5% or less,about 4.5% of less, about 4% or less, about 3.5% or less, about 3% orless, about 2.5% or less, about 2% or less, about 1.75% or less, about1.5% or less, about 1.25% or less, about 1% or less, about 0.75% orless, about 0.5% or less, about 0.25% or less, or about 0.1% or less,and all ranges and sub-ranges therebetween. Such percent-based averageoscillation amplitude may be exhibited by the article along wavelengthranges segments of about 50 nm, about 100 nm, about 200 nm or about 300nm, in the optical wavelength regime. For example, an article mayexhibit an average transmittance of about 85% along the wavelength rangefrom about 500 nm to about 600 nm, which is a wavelength range segmentof about 100 nm, within the optical wavelength regime. The article mayalso exhibit a percent-based oscillation amplitude of about 3% along thesame wavelength range (500 nm to about 600 nm), which means that alongthe wavelength range from 500 nm to 600 nm, the absolute(non-percent-based) oscillation amplitude is about 2.55 percentagepoints.

Substrate

The substrate 110 may be inorganic and may include an amorphoussubstrate, a crystalline substrate or a combination thereof. Thesubstrate 110 may be formed from man-made materials and/or naturallyoccurring materials. In some specific embodiments, the substrate 110 mayspecifically exclude plastic and/or metal substrates. In someembodiments, the substrate 110 may be organic and specificallypolymeric. Examples of suitable polymers include, without limitation:thermoplastics including polystyrene (PS) (including styrene copolymersand blends), polycarbonate (PC) (including copolymers and blends),polyesters (including copolymers and blends, includingpolyethyleneterephthalate and polyethyleneterephthalate copolymers),polyolefins (PO) and cyclicpolyolefins (cyclic-PO), polyvinylchloride(PVC), acrylic polymers including polymethyl methacrylate (PMMA)(including copolymers and blends), thermoplastic urethanes (TPU),polyetherimide (PEI) and blends of these polymers with each other. Otherexemplary polymers include epoxy, styrenic, phenolic, melamine, andsilicone resins.

In one or more embodiments, the substrate exhibits a refractive index inthe range from about 1.45 to about 1.55. In specific embodiments, thesubstrate 110 may exhibit an average strain-to-failure at a surface onone or more opposing major surface that is 0.5% or greater, 0.6% orgreater, 0.7% or greater, 0.8% or greater, 0.9% or greater, 1% orgreater, 1.1% or greater, 1.2% or greater, 1.3% or greater, 1.4% orgreater 1.5% or greater or even 2% or greater, as measured usingball-on-ring testing using at least 5, at least 10, at least 15, or atleast 20 samples. In specific embodiments, the substrate 110 may exhibitan average strain-to-failure at its surface on one or more opposingmajor surface of about 1.2%, about 1.4%, about 1.6%, about 1.8%, about2.2%, about 2.4%, about 2.6%, about 2.8%, or about 3% or greater.

Suitable substrates 110 may exhibit an elastic modulus (or Young'smodulus) in the range from about 30 GPa to about 120 GPa. In someinstances, the elastic modulus of the substrate may be in the range fromabout 30 GPa to about 110 GPa, from about 30 GPa to about 100 GPa, fromabout 30 GPa to about 90 GPa, from about 30 GPa to about 80 GPa, fromabout 30 GPa to about 70 GPa, from about 40 GPa to about 120 GPa, fromabout 50 GPa to about 120 GPa, from about 60 GPa to about 120 GPa, fromabout 70 GPa to about 120 GPa, and all ranges and sub-rangestherebetween.

In one or more embodiments, the substrate may be amorphous and mayinclude glass, which may be strengthened or non-strengthened. Examplesof suitable glass include soda lime glass, alkali aluminosilicate glass,alkali containing borosilicate glass and alkali aluminoborosilicateglass. In some variants, the glass may be free of lithia. In one or morealternative embodiments, the substrate 110 may include crystallinesubstrates such as glass ceramic substrates (which may be strengthenedor non-strengthened) or may include a single crystal structure, such assapphire. In one or more specific embodiments, the substrate 110includes an amorphous base (e.g., glass) and a crystalline cladding(e.g., sapphire layer, a polycrystalline alumina layer and/or or aspinel (MgAl₂O₄) layer).

The substrate 110 may be substantially planar or sheet-like, althoughother embodiments may utilize a curved or otherwise shaped or sculptedsubstrate. The substrate 110 may be substantially optically clear,transparent and free from light scattering. In such embodiments, thesubstrate may exhibit an average light transmission over the opticalwavelength regime of about 85% or greater, about 86% or greater, about87% or greater, about 88% or greater, about 89% or greater, about 90% orgreater, about 91% or greater or about 92% or greater. In one or morealternative embodiments, the substrate 110 may be opaque or exhibit anaverage light transmission over the optical wavelength regime of lessthan about 10%, less than about 9%, less than about 8%, less than about7%, less than about 6%, less than about 5%, less than about 4%, lessthan about 3%, less than about 2%, less than about 1%, or less thanabout 0%. In substrate 110 may optionally exhibit a color, such aswhite, black, red, blue, green, yellow, orange etc.

Additionally or alternatively, the physical thickness of the substrate110 may vary along one or more of its dimensions for aesthetic and/orfunctional reasons. For example, the edges of the substrate 110 may bethicker as compared to more central regions of the substrate 110. Thelength, width and physical thickness dimensions of the substrate 110 mayalso vary according to the application or use of the article 100.

The substrate 110 may be provided using a variety of differentprocesses. For instance, where the substrate 110 includes an amorphoussubstrate such as glass, various forming methods can include float glassprocesses and down-draw processes such as fusion draw and slot draw.

Once formed, a substrate 110 may be strengthened to form a strengthenedsubstrate. As used herein, the term “strengthened substrate” may referto a substrate that has been chemically strengthened, for examplethrough ion-exchange of larger ions for smaller ions in the surface ofthe substrate. However, other strengthening methods known in the art,such as thermal tempering, or utilizing a mismatch of the coefficient ofthermal expansion between portions of the substrate to createcompressive stress and central tension regions, may be utilized to formstrengthened substrates.

Where the substrate is chemically strengthened by an ion exchangeprocess, the ions in the surface layer of the substrate are replacedby—or exchanged with—larger ions having the same valence or oxidationstate. Ion exchange processes are typically carried out by immersing asubstrate in a molten salt bath containing the larger ions to beexchanged with the smaller ions in the substrate. It will be appreciatedby those skilled in the art that parameters for the ion exchangeprocess, including, but not limited to, bath composition andtemperature, immersion time, the number of immersions of the substratein a salt bath (or baths), use of multiple salt baths, additional stepssuch as annealing, washing, and the like, are generally determined bythe composition of the substrate and the desired compressive stress(CS), depth of compressive stress layer (or depth of layer) of thesubstrate that result from the strengthening operation. By way ofexample, ion exchange of alkali metal-containing glass substrates may beachieved by immersion in at least one molten bath containing a salt suchas, but not limited to, nitrates, sulfates, and chlorides of the largeralkali metal ion. The temperature of the molten salt bath typically isin a range from about 380° C. up to about 450° C., while immersion timesrange from about 15 minutes up to about 40 hours. However, temperaturesand immersion times different from those described above may also beused.

In addition, non-limiting examples of ion exchange processes in whichglass substrates are immersed in multiple ion exchange baths, withwashing and/or annealing steps between immersions, are described in U.S.patent application Ser. No. 12/500,650, filed Jul. 10, 2009, by DouglasC. Allan et al., entitled “Glass with Compressive Surface for ConsumerApplications” and claiming priority from U.S. Provisional PatentApplication No. 61/079,995, filed Jul. 11, 2008, in which glasssubstrates are strengthened by immersion in multiple, successive, ionexchange treatments in salt baths of different concentrations; and U.S.Pat. No. 8,312,739, by Christopher M. Lee et al., issued on Nov. 20,2012, and entitled “Dual Stage Ion Exchange for Chemical Strengtheningof Glass,” and claiming priority from U.S. Provisional PatentApplication No. 61/084,398, filed Jul. 29, 2008, in which glasssubstrates are strengthened by ion exchange in a first bath is dilutedwith an effluent ion, followed by immersion in a second bath having asmaller concentration of the effluent ion than the first bath. Thecontents of U.S. patent application Ser. No. 12/500,650 and U.S. Pat.No. 8,312,739 are incorporated herein by reference in their entirety.

The degree of chemical strengthening achieved by ion exchange may bequantified based on the parameters of central tension (CT), surface CS,and depth of layer (DOL). Surface CS may be measured near the surface orwithin the strengthened glass at various depths. A maximum CS value mayinclude the measured CS at the surface (CSs) of the strengthenedsubstrate. The CT, which is computed for the inner region adjacent thecompressive stress layer within a glass substrate, can be calculatedfrom the CS, the physical thickness t, and the DOL. CS and DOL aremeasured using those means known in the art. Such means include, but arenot limited to, measurement of surface stress (FSM) using commerciallyavailable instruments such as the FSM-6000, manufactured by Luceo Co.,Ltd. (Tokyo, Japan), or the like, and methods of measuring CS and DOLare described in ASTM 1422C-99, entitled “Standard Specification forChemically Strengthened Flat Glass,” and ASTM 1279.19779 “Standard TestMethod for Non-Destructive Photoelastic Measurement of Edge and SurfaceStresses in Annealed, Heat-Strengthened, and Fully-Tempered Flat Glass,”the contents of which are incorporated herein by reference in theirentirety. Surface stress measurements rely upon the accurate measurementof the stress optical coefficient (SOC), which is related to thebirefringence of the glass substrate. SOC in turn is measured by thosemethods that are known in the art, such as fiber and four point bendmethods, both of which are described in ASTM standard C770-98 (2008),entitled “Standard Test Method for Measurement of Glass Stress-OpticalCoefficient,” the contents of which are incorporated herein by referencein their entirety, and a bulk cylinder method. The relationship betweenCS and CT is given by the expression (1):

CT=(CS·DOL)/(t−2 DOL)   (1),

wherein t is the physical thickness (μm) of the glass article. Invarious sections of the disclosure, CT and CS are expressed herein inmegaPascals (MPa), physical thickness t is expressed in eithermicrometers (μm) or millimeters (mm) and DOL is expressed in micrometers(μm).

In one embodiment, a strengthened substrate 110 can have a surface CS of250 MPa or greater, 300 MPa or greater, e.g., 400 MPa or greater, 450MPa or greater, 500 MPa or greater, 550 MPa or greater, 600 MPa orgreater, 650 MPa or greater, 700 MPa or greater, 750 MPa or greater or800 MPa or greater. The strengthened substrate may have a DOL of 10 μmor greater, 15 μm or greater, 20 μm or greater (e.g., 25 μm, 30 μm, 35μm, 40 μm, 45 μm, 50 μm or greater) and/or a CT of 10 MPa or greater, 20MPa or greater, 30 MPa or greater, 40 MPa or greater (e.g., 42 MPa, 45MPa, or 50 MPa or greater) but less than 100 MPa (e.g., 95, 90, 85, 80,75, 70, 65, 60, 55 MPa or less). In one or more specific embodiments,the strengthened substrate has one or more of the following: a surfaceCS greater than 500 MPa, a DOL greater than 15 μm, and a CT greater than18 MPa.

Example glasses that may be used in the substrate may include alkalialuminosilicate glass compositions or alkali aluminoborosilicate glasscompositions, though other glass compositions are contemplated. Suchglass compositions are capable of being chemically strengthened by anion exchange process. One example glass composition comprises SiO₂, B₂O₃and Na₂O, where (SiO₂+B₂O₃)≥66 mol. %, and Na₂O≥9 mol. %. In anembodiment, the glass composition includes at least 6 wt.% aluminumoxide. In a further embodiment, the substrate includes a glasscomposition with one or more alkaline earth oxides, such that a contentof alkaline earth oxides is at least 5 wt.%. Suitable glasscompositions, in some embodiments, further comprise at least one of K₂O,MgO, and CaO. In a particular embodiment, the glass compositions used inthe substrate can comprise 61-75 mol. % SiO2; 7-15 mol. % Al₂O₃; 0-12mol. % B₂O₃; 9-21 mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. % MgO; and 0-3mol. % CaO.

A further example glass composition suitable for the substratecomprises: 60-70 mol. % SiO₂; 6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15mol. % Li₂O; 0-20 mol. % Na₂O; 0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10mol. % CaO; 0-5 mol. % ZrO₂; 0-1 mol. % SnO₂; 0-1 mol. % CeO₂; less than50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 12 mol. %(Li₂O+Na₂O+K₂O)≤20 mol. % and 0 mol. %≤(MgO+CaO)≤10 mol. %.

A still further example glass composition suitable for the substratecomprises: 63.5-66.5 mol. % SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃;0-5 mol. % Li₂O; 8-18 mol. % Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5mol. % CaO; 0-3 mol. % ZrO₂; 0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. %CeO₂; less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 14 mol.%≤(Li₂O+Na₂O+K₂O)≤18 mol. % and 2 mol. %≤(MgO+CaO)≤7 mol. %.

In a particular embodiment, an alkali aluminosilicate glass compositionsuitable for the substrate comprises alumina, at least one alkali metaland, in some embodiments, greater than 50 mol. % SiO₂, in otherembodiments at least 58 mol. % SiO₂, and in still other embodiments atleast 60 mol. % SiO₂, wherein the ratio

${\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1},$

where in the ratio the components are expressed in mol. % and themodifiers are alkali metal oxides. This glass composition, in particularembodiments, comprises: 58-72 mol. % SiO₂; 9-17 mol. % Al₂O₃; 2-12 mol.% B₂O₃; 8-16 mol. % Na₂O; and 0-4 mol. % K₂O, wherein the ratio

$\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1.$

In still another embodiment, the substrate may include an alkalialuminosilicate glass composition comprising: 64-68 mol. % SiO₂; 12-16mol. % Na₂O; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃; 2-5 mol. % K₂O; 4-6mol. % MgO; and 0-5 mol. % CaO, wherein: 66 mol. %≤SiO₂+B₂O₃+CaO≤69 mol.%; Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %;(Na₂O+B₂O₃)—Al₂O₃≤2 mol. %; 2 mol. %≤Na₂O—Al₂O₃≤6 mol. %; and 4 mol.%≤(Na₂O+K₂O)—Al₂O₃≤10 mol. %.

In an alternative embodiment, the substrate may comprise an alkalialuminosilicate glass composition comprising: 2 mol % or more of Al₂O₃and/or ZrO₂, or 4 mol % or more of Al₂O₃ and/or ZrO₂.

Where the substrate 110 includes a crystalline substrate, the substratemay include a single crystal, which may include Al₂O₃. Such singlecrystal substrates are referred to as sapphire. Other suitable materialsfor a crystalline substrate include polycrystalline alumina layer and/orspinel (MgAl₂O₄).

Optionally, the crystalline substrate 110 may include a glass ceramicsubstrate, which may be strengthened or non-strengthened. Examples ofsuitable glass ceramics may include Li₂O—Al₂O₃—SiO₂ system (i.e.LAS-System) glass ceramics, MgO—Al₂O₃—SiO₂ system (i.e. MAS-System)glass ceramics, and/or glass ceramics that include a predominant crystalphase including β-quartz solid solution, β-spodumene ss, cordierite, andlithium disilicate. The glass ceramic substrates may be strengthenedusing the chemical strengthening processes disclosed herein. In one ormore embodiments, MAS-System glass ceramic substrates may bestrengthened in Li₂SO₄ molten salt, whereby an exchange of 2Li⁺ for Mg²⁺can occur.

The substrate 110 according to one or more embodiments can have aphysical thickness ranging from about 100 μm to about 5 mm. Examplesubstrate 110 physical thicknesses range from about 100 μm to about 500μm (e.g., 100, 200, 300, 400 or 500 μm). Further example substrate 110physical thicknesses range from about 500 μm to about 1000 μm (e.g.,500, 600, 700, 800, 900 or 1000 μm). The substrate 110 may have aphysical thickness greater than about 1 mm (e.g., about 2, 3, 4, or 5mm). In one or more specific embodiments, the substrate 110 may have aphysical thickness of 2 mm or less or less than 1 mm. The substrate 110may be acid polished or otherwise treated to remove or reduce the effectof surface flaws.

Optical Film

As shown in FIG. 5-6, the optical film 120 may include a plurality oflayers 130, 140, 150. Additional layers may also be included in opticalfilm 120. Moreover, in some embodiments, one or more films or layers maybe disposed on the opposite side of the substrate 110 from the opticalfilm 120 (i.e., on major surface 114).

The physical thickness of the optical film 120 may be in the range fromabout 0.1 μm to about 3 μm. In some instances, the physical thickness ofthe optical film 120 may be in the range from about 0.1 μm to about 2.9μm, from about 0.1 μm to about 2.8 μm, from about 0.1 μm to about 2.7μm, from about 0.1 μm to about 2.6 μm, from about 0.1 μm to about 2.5μm, from about 0.1 μm to about 2.4 μm, from about 0.1 μm to about 2.3μm, from about 0.1 μm to about 2.2 μm, from about 0.1 μm to about 2.1μm, from about 0.1 μm to about 2 μm, from about 0.5 μm to about 3 μm,from about 1 μm to about 3μm, from about 1.1 μm to about 3 μm, fromabout 1.2 μm to about 3 μm, from about 1.3 μm to about 3 μm, from about1.4 μm to about 3 μm, or from about 1.5 μm to about 3 μm, and all rangesand sub-ranges therebetween.

The optical film 120 may exhibit a maximum hardness of greater thanabout 5 GPa, as measured on the coated surface 101, by the BerkovichIndenter Hardness Test. For example, the optical film 120 may exhibit ahardness in the range from about 6 GPa to about 30 GPa, from about 7 GPato about 30 GPa, from about 8 GPa to about 30 GPa, from about 9 GPa toabout 30 GPa, from about 10 GPa to about 30 GPa, from about 12 GPa toabout 30 GPa, from about 5 GPa to about 28 GPa, from about 5 GPa toabout 26 GPa, from about 5 GPa to about 24 GPa, from about 5 GPa toabout 22 GPa, from about 5 GPa to about 20 GPa, from about 12 GPa toabout 25 GPa, from about 15 GPa to about 25 GPa, from about 16 GPa toabout 24 GPa, from about 18 GPa to about 22 GPa and all ranges andsub-ranges therebetween. Such hardness values may be exhibited atindentation depths of about 50 nm or greater or about 100 nm or greater.In one or more embodiments, the indentation depths may be in the rangefrom about 100 nm to about 300 nm, from about 100 nm to about 400 nm,from about 100 nm to about 500 nm, from about 100 nm to about 600 nm,from about 200 nm to about 300 nm, from about 200 nm to about 400 nm,from about 200 nm to about 500 nm, or from about 200 nm to about 600 nm.

In one or more embodiments, the optical film includes an opticalinterference layer 130 disposed on major surface 112 of the substrate110, a scratch-resistant layer 140 disposed on the optical interferencelayer 130 and an optional capping layer 150 disposed on the scratchresistant layer 140. In the embodiment shown, the optical interferencelayer 130 is disposed between the substrate 110 and thescratch-resistant layer 140, thus modifying the interface between thesubstrate 110 and the scratch-resistant layer 140.

The optical film or any one or of the layers in the optical film mayexhibit an extinction coefficient (at a wavelength of about 400 nm) ofabout 10′ or less.

The optical interference layer 130 may include two or more sub-layers.In one or more embodiments, the two or more sub-layers may becharacterized as having a different refractive index. Unless otherwisestated, refractive index values described herein are with reference awavelength of about 550 nm. In embodiment, the optical interferencelayer 130 includes a first low RI sub-layer and a second high RIsub-layer. The difference in the refractive index of the first low RIsub-layer and the second high RI sub-layer may be about 0.01 or greater,0.05 or greater, 0.1 or greater or even 0.2 or greater.

As shown in FIG. 6, the optical interference layer may include aplurality of sub-layer sets (131). A single sub-layer set may include afirst low RI sub-layer and a second high RI sub-layer. For example,sub-layer set 131 includes a first low RI sub-layer 131A and a secondhigh RI sub-layer 131B. In some embodiments, the optical interferencelayer may include a plurality of sub-layer sets such that the first lowRI sub-layer (designated for illustration as “L”) and the second high RIsub-layer (designated for illustration as “H”) may be provide thefollowing sequence of sub-layers: L/H/L/H or H/L/H/L, such that thefirst low RI sub-layer and the second high RI sub-layer appear toalternate along the physical thickness of the optical interferencelayer. In the example in FIG. 6, the optical interference layer 130includes three sub-layer sets. In some embodiments, the opticalinterference layer 130 may include up to 10 sub-layer sets. For example,the optical interference layer 130 may include from about 2 to about 12sub-layer sets, from about 3 to about 8 sub-layer sets, from about 3 toabout 6 sub-layer sets.

In some embodiments, the optical interference layer may include one ormore third sub-layers. The third sub-layer(s) may have a low RI, a highRI or a medium RI. In some embodiments, the third sub-layer(s) may havethe same RI as the first low RI sub-layer 131A or the second high RIsub-layer 131B. In other embodiments, the third sub-layer(s) may have amedium RI that is between the RI of the first low RI sub-layer 131A andthe RI of the second high RI sub-layer 131B. The third sub-layer(s) maybe disposed between the plurality of sub-layer sets and thescratch-resistant layer 140 (see FIG. 12, 231C) or between the substrateand the plurality of sub-layer sets (see FIG. 12, 231D). Alternatively,the third sub-layer may be included in the plurality of sub-layer sets(not shown). The third sub-layer may be provided in the opticalinterference layer in the following exemplary configurations:L_(third sub-layer)/H/L/H/L; H_(third sub-layer)/L/H/L/H;L/H/L/H/L_(third sub-layer); H/L/H/L/H_(third sub-layer);L_(third sub-layer)/H/L/H/L/H_(third sub-layer);H_(third sub-layer)/L/H/L/H/L_(third sub-layer);L_(third sub-layer)/L/H/L/H; H_(third sub-layer)/H/L/H/L;H/L/H/L/L_(third sub-layer); L/H/L/H/H_(third sub-layer);L_(third sub-layer)/L/H/L/H/H_(third sub-layer);H_(third sub-layer)//H/L/H/L/L_(third sub-layer); L/M/H/L/M/H;H/M/L/H/M/L; M/L/H/L/M; and other combinations. In these configurations,“L” without any subscript refers to the first low RI sub-layer and “H”without any subscript refers to the second high RI sub-layer. Referenceto “L_(third sub-layer)” refers to a third sub-layer having a low RI,“H_(third sub-layer)” refers to a third sub-layer having a high RI and“M” refers to a third sub-layer having a medium RI.

As used herein, the terms “low RI”, “high RI” and “medium RI” refer tothe relative values for the RI to another (e.g., low RI<medium RI<highRI). In one or more embodiments, the term “low RI” when used with thefirst low RI sub-layer or with the third sub-layer, includes a rangefrom about 1.3 to about 1.7 (e.g., about 1.4 to about 1.6, or about1.46). In one or more embodiments, the term “high RI” when used with thesecond high RI sub-layer or with the third sub-layer, includes a rangefrom about 1.6 to about 2.5 (e.g., about 1.8 to about 2.1, or about 1.9to about 2.0). In some embodiments, the term “medium RI” when used withthe third sub-layer, includes a range from about 1.55 to about 1.8. Insome instances, the ranges for low RI, high RI and medium RI mayoverlap; however, in most instances, the sub-layers of the opticalinterference layer have the general relationship regarding RI of: lowRI<medium RI<high RI.

Exemplary materials suitable for use in the optical interference layer130 include: SiO₂, Al₂O₃, GeO₂, SiO, AlO_(x)N_(y), AlN, Si₃N₄,SiO_(x)N_(y), Si_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, TiO₂, ZrO₂, TiN,MgO, MgF₂, BaF₂, CaF₂, SnO₂, HfO₂, Y₂O₃, MoO₃, DyF₃, YbF₃, YF₃, CeF₃,polymers, fluoropolymers, plasma-polymerized polymers, siloxanepolymers, silsesquioxanes, polyimides, fluorinated polyimides,polyetherimide, polyethersulfone, polyphenylsulfone, polycarbonate,polyethylene terephthalate, polyethylene naphthalate, acrylic polymers,urethane polymers, polymethylmethacrylate, other materials cited belowas suitable for use in a scratch-resistant layer, and other materialsknown in the art. Some examples of suitable materials for use in thefirst low RI sub-layer include SiO₂, Al₂O₃, GeO₂, SiO, AlO_(x)N_(y),SiO_(x)N_(y), Si_(u)Al_(v)O_(x)N_(y), MgO, MgF₂, BaF₂, CaF₂, DyF₃, YbF₃,YF₃, and CeF₃. Some examples of suitable materials for use in the secondhigh RI sub-layer include Si_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, AlN,Si₃N₄, AlO_(x)N_(y), SiO_(x)N_(y), HfO₂, TiO₂, ZrO₂, Y₂O₃, Al₂O₃, andMoO₃.

In one or more embodiments at least one of the sub-layer(s) of theoptical interference layer may include a specific optical thicknessrange. As used herein, the term “optical thickness” is determined by(n*d), where “n” refers to the RI of the sub-layer and “d” refers to thephysical thickness of the sub-layer. In one or more embodiments, atleast one of the sub-layers of the optical interference layer mayinclude an optical thickness in the range from about 2 nm to about 200nm, from about 10 nm to about 100 nm, or from about 15 nm to about 100nm. In some embodiments, all of the sub-layers in the opticalinterference layer 130 may each have an optical thickness in the rangefrom about 2 nm to about 200 nm, from about 10 nm to about 100 nm orfrom about 15 nm to about 100 nm. In some cases, at least one sub-layerof the optical interference layer 130 has an optical thickness of about50 nm or greater. In some cases, each of the first low RI sub-layershave an optical thickness in the range from about 2 nm to about 200 nm,from about 10 nm to about 100 nm, or from about 15 nm to about 100 nm.In other cases, each of the second high RI sub-layers have an opticalthickness in the range from about 2 nm to about 200 nm, from about 10 nmto about 100 nm, or from about 15 nm to about 100 nm. In yet othercases, each of the third sub-layers have an optical thickness in therange from about 2 nm to about 200 nm, from about 10 nm to about 100 nm,or from about 15 nm to about 100 nm.

In one or more embodiments, the optical interference layer 130 has aphysical thickness of about 800 nm or less. The optical interferencelayer 130 may have a physical thickness in the range from about 10 nm toabout 800 nm, from about 50 nm to about 800 nm, from about 100 nm toabout 800 nm, from about 150 nm to about 800 nm, from about 200 nm toabout 800 nm, from about 10 nm to about 750 nm, from about 10 nm toabout 700 nm, from about 10 nm to about 650 nm, from about 10 nm toabout 600 nm, from about 10 nm to about 550 nm, from about 10 nm toabout 500 nm, from about 10 nm to about 450 nm, from about 10 nm toabout 400 nm, from about 10 nm to about 350 nm, from about 10 nm toabout 300 nm, from about 50 to about 300, from about 100 nm to about 200nm, from about 125 nm to about 200 nm, from about 150 nm to about 190nm, or from about 160 nm to about 180 nm, and all ranges and sub-rangestherebetween.

In some embodiments, the optical interference layer exhibits an averagelight reflectance of about 2% or less, 1.5% or less, 0.75% or less, 0.5%or less, 0.25% or less, 0.1% or less, or even 0.05% or less over theoptical wavelength regime, when measured in an immersed state. As usedherein, the phrase “immersed state” includes the measurement of theaverage reflectance by subtracting or otherwise removing reflectionscreated by the article at interfaces other than those involving theoptical interference layer. In some instances, the optical interferencelayer may exhibit such average light reflectance over other wavelengthranges such as from about 450 nm to about 650 nm, from about 420 nm toabout 680 nm, from about 420 nm to about 740 nm, from about 420 nm toabout 850 nm, or from about 420 nm to about 950 nm. In some embodiments,the optical interference layer exhibits an average light transmission ofabout 90% or greater, 92% or greater, 94% or greater, 96% or greater, or98% or greater, over the optical wavelength regime.

The optical interference layer 130 of the embodiments described hereinmay be distinguished from layers that have a monotonic refractive indexgradient. Articles that include the optical interference layer 130between a scratch-resistant layer 140 and the substrate 110 exhibitimproved optical performance (e.g., high average light transmission, lowaverage light reflectance, low color shift as described herein), whilereducing the physical thickness of the optical film 120. Monotonicrefractive index gradient layers provide similar optical properties butmay require greater physical thicknesses.

The scratch-resistant layer 140 of one or more embodiments may includean inorganic carbide, nitride, oxide, diamond-like material, orcombination of these. Examples of suitable materials for thescratch-resistant layer 140 include metal oxides, metal nitrides, metaloxynitride, metal carbides, metal oxycarbides, and/or combinationsthereof combination thereof. Exemplary metals include B, Al, Si, Ti, V,Cr, Y, Zr, Nb, Mo, Sn, Hf, Ta and W. Specific examples of materials thatmay be utilized in the scratch-resistant layer 140 may include Al₂O₃,AlN, AlO_(x)N_(y), Si₃N₄, SiO_(x)N_(y), Si_(u)Al_(v)O_(x)N_(y), diamond,diamond-like carbon, Si_(x)C_(y), Si_(x)O_(y)C_(z), ZrO₂, TiO_(x)N_(y)and combinations thereof.

The scratch resistant layer may also comprise nanocomposite materials,or materials with a controlled microstructure to improve hardness,toughness, or abrasion/wear resistance. For example the scratchresistant layer may comprise nanocrystallites in the size range fromabout 5 nm to about 30 nm. In embodiments, the scratch resistant layermay comprise transformation-toughened zirconia, partially stabilizedzirconia, or zirconia-toughened alumina. In embodiments, thescratch-resistant layer exhibits a fracture toughness value greater thanabout 1 MPa√m and simultaneously exhibits a hardness value greater thanabout 8 GPa, as measured by the Berkovich Indenter Hardness Test.

The composition of the scratch-resistant layer 140 may be modified toprovide specific properties (e.g., hardness, refractive index etc.). Inone or more embodiments, the scratch resistant layer may include AlOxNythat includes up to about 60 atomic % aluminum, up to about 20 atomic %oxygen and up to about 40 atomic % nitrogen. In some embodiments, theAlOxNy material may include silicon. In some embodiments, the AlOxNymaterial may include aluminum in an amount in the range from about 45atomic % to about 55 atomic % (e.g., about 50 atomic %), oxygen in anamount in the range from about 12 atomic % to about 20 atomic % (e.g.,about 15 atomic % to about 17 atomic %), and nitrogen in an amount inthe range from about 30 atomic % to about 35 atomic % (e.g., about 32atomic % or about 33 atomic %).

In some instances the amount of oxygen in the scratch resistant layermay be controlled to form larger crystal sizes or smaller crystal sizes.In other words, the amount of oxygen may be modified to provide adesired crystallinity and/or crystal size (or size range) of the scratchresistant layer. The amount of nitrogen may be controlled to provide adesired hardness, as measured by the Berkovich Indenter Hardness Test.An increased amount of nitrogen relative to oxygen may provide a scratchresistant layer and thus an article including the same, which exhibitshigher hardness than such a layer or article that includes less nitrogenrelative to the amount of oxygen. Moreover, the amount of nitrogen tooxygen may alter the refractive index and thus may influence thetransmittance and color shift of the article.

In one or more embodiments, the scratch-resistant layer 140 exhibits ahardness in the range from about 5 GPa to about 30 GPa as measured bythe Berkovich Indenter Hardness Test (measured from the major surface ofthe scratch-resistant layer). In one or more embodiments, thescratch-resistant layer 140 exhibits a hardness in the range from about6 GPa to about 30 GPa, from about 7 GPa to about 30 GPa, from about 8GPa to about 30 GPa, from about 9 GPa to about 30 GPa, from about 10 GPato about 30 GPa, from about 12 GPa to about 30 GPa, from about 5 GPa toabout 28 GPa, from about 5 GPa to about 26 GPa, from about 5 GPa toabout 24 GPa, from about 5 GPa to about 22 GPa, from about 5 GPa toabout 20 GPa, from about 12 GPa to about 25 GPa, from about 15 GPa toabout 25 GPa, from about 16 GPa to about 24 GPa, from about 18 GPa toabout 22 GPa and all ranges and sub-ranges therebetween. In one or moreembodiments, the scratch-resistant layer 140 may exhibit a hardness thatis greater than 15 GPa, greater than 20 GPa, or greater than 25 GPa. Inone or more embodiments, the scratch-resistant layer exhibits a hardnessin the range from about 15 GPa to about 150 GPa, from about 15 GPa toabout 100 GPa, or from about 18 GPa to about 100 GPa. These hardnessvalues may be present at indentation depths of about 50 nm or greater,or about 100 nm or greater (e.g., in the range from about 100 nm toabout 300 nm, from about 100 nm to about 400 nm, from about 100 nm toabout 500 nm, from about 100 nm to about 600 nm, from about 200 nm toabout 300 nm, from about 200 nm to about 400 nm, from about 200 nm toabout 500 nm, or from about 200 nm to about 600 nm).

The physical thickness of the scratch-resistant layer 140 may be in therange from about 1.5 μm to about 3 μm. In some embodiments, the physicalthickness of the scratch-resistant layer 140 may be in the range fromabout 1.5 μm to about 3μm, from about 1.5 μm to about 2.8 μm, from about1.5 μm to about 2.6 μm, from about 1.5 μm to about 2.4 μm, from about1.5 μm to about 2.2 μm, from about 1.5 μm to about 2 μm, from about 1.6μm to about 3 μm, from about 1.7 μm to about 3 μm, from about 1.8 μm toabout 3 μm, from about 1.9 μm to about 3 μm, from about 2 μm to about 3μm, from about 2.1 μm to about 3 μm, from about 2.2 μm to about 3 μm,from about 2.3 μm to about 3 μm, and all ranges and sub-rangestherebetween. In some embodiments, the physical thickness of thescratch-resistant layer 140 may be in the range from about 0.1 μm toabout 2 μm, or from about 0.1 μm to about 1 μm, or from 0.2 μm to about1 μm.

In one or more embodiments, the scratch-resistant layer 140 has arefractive index of about 1.6 or greater. In some instances, therefractive index of the scratch-resistant layer 140 may be about 1.65 orgreater, 1.7 or greater, 1.8 or greater, 1.9 or greater, 2 or greater,or 2.1 or greater (e.g., in the range from about 1.8 to about 2.1, orfrom about 1.9 to about 2.0). The scratch-resistant layer may have arefractive index that is greater than the refractive index of thesubstrate 110. In specific embodiments, the scratch-resistant layer hasa refractive index that is about 0.05 index units greater or about 0.2index units greater than the refractive index of the substrate, whenmeasured at a wavelength of about 550 nm.

The capping layer 150 of one or more embodiments may include a lowrefractive index material, such as SiO₂, Al₂O₃, GeO₂, SiO, AlO_(x)N_(y),SiO_(x)N_(y), Si_(u)Al_(v)O_(x)N_(y), MgO, MgF₂, BaF₂, CaF₂, DyF₃, YbF₃,YF₃, and CeF₃ and other such materials. The physical thickness of thecapping layer may be in the range from about 0 to about 100 nm, fromabout 0.1 nm to about 50 nm, from about 1 nm to about 50 nm, from about5 nm to about 50 nm, from about 10 nm to about 50 nm, from about 0 nm toabout 40, from about 0 nm to about 30, from about 0 nm to about 20 nm,from about 0 nm to about 10 nm, from about 0.1 nm to about 15 nm, fromabout 0.1 nm to about 12 nm, from about 0.1 nm to about 10 nm, fromabout 0.1 nm to about 8 nm, from about 4 nm to about 30 nm, from about 4nm to about 20 nm, from about 8 nm to about 12 nm, from about 9 nm toabout 10 nm, and all ranges and sub-ranges therebetween. The refractiveindex of the capping layer may be in the range from about 1.4 to about1.6 (e.g., about 1.46). The capping layer may exhibit an intrinsichardness in the range from about 7 GPa to about 10 GPa, as measured bythe Berkovich Indenter Hardness Test (as measured on the surface of alayer of the same material of the capping layer, formed in the samemanner, but having a thickness of about 1 micrometer or greater).

In one or more embodiments, the article has a refractive index of about1.7 or greater at the coated surface 101, which may include the cappinglayer. The capping layer 150 may formed using silane-based low-frictionmaterials, including fluorosilane, alkyl silane, silsesquioxane, and thelike, either by liquid deposition or vapor deposition methods. In one ormore embodiments, the capping layer may comprise two or more materialsor two or more sub-layers (e.g., 4 sub-layers or 6 sub-layers). Thecapping layer may provide an anti-reflective function especially wheremultiple sub-layers are utilized. The sub-layers may include differentrefractive indices and may include layers with high refractive indices(H) and low refractive indices (L) where “high” and “low” are withrespect to one another and within known ranges for anti-reflectivefilms. The sub-layers may be arranged so that high and low refractiveindex sub-layers alternate. The materials or sub-layers can include, forexample SiO₂ or SiO_(x)N_(y). In such embodiments, the one or moresub-layers can have a thickness each or combined in the range from about4 nm to about 50 nm. In some embodiments, the capping layer 150 mayinclude a silane-based low-friction sub-layer having a thickness in therange from about 0.1 nm to about 20 nm, disposed on underlyingsub-layers of the capping layer (e.g., the SiO₂ and/or SiO_(x)N_(y)layer(s)).

In some embodiments, the optical interference layer 130 may alsocomprise a crack mitigating layer. This crack mitigating layer maysuppress or prevent crack bridging between the scratch resistant layer140 and the substrate 110, thus modifying or improving the mechanicalproperties or strength of the article. Embodiments of crack mitigatinglayers are further described in U.S. patent application Ser. Nos.14/052,055, 14/053,093 and 14/053,139, which are incorporated herein byreference. The crack mitigating layer may comprise crack bluntingmaterials, crack deflecting materials, crack arresting materials, toughmaterials, or controlled-adhesion interfaces. The crack mitigating layermay comprise polymeric materials, nanoporous materials, metal oxides,metal fluorides, metallic materials, or other materials mentioned hereinfor use in either the optical interference layer 130 or the scratchresistant layer 140. The structure of the crack mitigating layer may bea multilayer structure, wherein the multilayer structure is designed todeflect, suppress, or prevent crack propagation while simultaneouslyproviding the optical interference benefits described herein. The crackmitigating layer may include nanocrystallites, nanocomposite materials,transformation toughened materials, multiple layers of organic material,multiple layers of inorganic material, multiple layers ofinterdigitating organic and inorganic materials, or hybridorganic-inorganic materials. The crack mitigating layer may have astrain to failure that is greater than about 2%, or greater than about10%. These crack mitigating layers can also be combined separately withthe substrate, scratch resistant layer, and optical interferencelayer(s) described herein; it is not strictly required that the crackmitigating layer is simultaneously acting as an optical interferencelayer. In embodiments, the crack mitigating layer can perform itsfunction in the presence or in the absence of an optical interferencelayer (and vice versa). The design of the optical interference layer canbe adjusted, if needed, to accommodate the presence of a crackmitigating layer.

The crack mitigating layer may include tough or nanostructuredinorganics, for example, zinc oxide, certain Al alloys, Cu alloys,steels, or stabilized tetragonal zirconia (including transformationtoughened, partially stabilized, yttria stabilized, ceria stabilized,calcia stabilized, and magnesia stabilized zirconia); zirconia-toughenedceramics (including zirconia toughened alumina); ceramic-ceramiccomposites; carbon-ceramic composites; fiber- or whisker-reinforcedceramics or glass-ceramics (for example, SiC or Si₃N₄ fiber- orwhisker-reinforced ceramics); metal-ceramic composites; porous ornon-porous hybrid organic-inorganic materials, for example,nanocomposites, polymer-ceramic composites, polymer-glass composites,fiber-reinforced polymers, carbon-nanotube- or graphene-ceramiccomposites, silsesquioxanes, polysilsesquioxanes, or “ORMOSILs”(organically modified silica or silicate), and/or a variety of porous ornon-porous polymeric materials, for example siloxanes, polysiloxanes,polyacrylates, polyacrylics, PI (polyimides), fluorinated polyimide,polyamides, PAI (polyamideimides), polycarbonates, polysulfones, PSU orPPSU (polyarylsulfones), fluoropolymers, fluoroelastomers, lactams,polycylic olefins, and similar materials, including, but not limited toPDMS (polydimethylsiloxane), PMMA (poly(methyl methacrylate)), BCB(benzocyclobutene), PEI (polyethyletherimide), poly(arylene ethers) suchas PEEK (poly-ether-ether-ketone), PES (polyethersulfone) and PAR(polyarylate) , PET (polyethylene terephthalate), PEN (polyethylenenapthalate=poly(ethylene-2,6-napthalene dicarboxylate), FEP (fluorinatedethylene propylene), PTFE (polytetrafluoroethylene), PFA (perfluroalkoxypolymer, e.g., trade names Teflon®, Neoflon®) and similar materials.Other suitable materials include modified polycarbonates, some versionsof epoxies, cyanate esters, PPS (polyphenylsulfides), polyphenylenes,polypyrrolones, polyquinoxalines, and bismaleimides.

The physical and/or optical thicknesses of the layers of the opticalfilm 120 can be adjusted to achieve desired optical and mechanicalproperties (e.g., hardness). For example, the scratch-resistant layer140 may be can be made thinner, for example in the range from about 100nm to about 500 nm, while still providing some resistance to scratch,abrasion, or damage events (including drop events of the article ontohard surfaces such as asphalt, cement, or sandpaper). The capping layerphysical and/or optical thickness can also be adjusted. The cappinglayer may be included when even lower total reflection is desired. Thecapping layer may also be included to further tune color of the article.For example, the optical films described herein minimize color shiftwith changing incidence illumination angle in a* or b* coordinates, butmay also exhibit a slight slope to the reflectance spectra. A cappinglayer 150 may be included in the optical film 120 and the physicaland/or optical thickness of the capping layer may be adjusted slightly(e.g., from about 10 nm to about 14 nm) to provide an even flatterreflectance spectrum (or a reflectance spectrum with oscillations havingeven smaller amplitudes) across the optical wavelength regime.

The optical film 120 may be formed using various deposition methods suchas vacuum deposition techniques, for example, chemical vapor deposition(e.g., plasma enhanced chemical vapor deposition, low-pressure chemicalvapor deposition, atmospheric pressure chemical vapor deposition, andplasma-enhanced atmospheric pressure chemical vapor deposition),physical vapor deposition (e.g., reactive or nonreactive sputtering orlaser ablation), thermal or e-beam evaporation and/or atomic layerdeposition. One or more layers of the optical film 120 may includenano-pores or mixed-materials to provide specific refractive indexranges or values.

The physical thicknesses of the layers or sub-layers of the optical film120 may vary by less than about 10 nm, less than about 5 nm, less thanabout 1 nm or less than about 0.5 nm (representing the range of sixstandard deviations from the target value) to achieve the maximumtargeted repeatability (e.g., a* and b* variations no greater than+/−0.2 for reflected F2 illumination). In some embodiments, largervariations in physical thicknesses of the layers can be tolerated whilestill achieving the desired targets of the invention for someapplications (e.g., a* and b* variations no greater than +/−2.0 forreflected F2 illumination).

High-angle optical performance may be improved in some embodiments byadding additional layers to the optical film 120 and/or the article 100.In some cases, these additional layers can extend the wavelengths atwhich the reflectance spectrum has low amplitude oscillations (e.g.,into the near-IR wavelengths, such as to 800 nm, 900 nm, or even 1000nm). This leads to lower oscillations and lower color at high incidenceangles, because generally the entire reflectance spectra of the articleshifts to shorter wavelengths at higher light incidence angles. In somecases, this extended-band performance can be achieved by adjusting theinterference layer design, for example by allowing a higher oscillationamplitude to achieve a wider-wavelength-band of low oscillations,without necessarily adding more layers. This extended-band orwide-wavelength-band of low oscillations (correlated to an extended bandof low reflectance for the interference layers) can also be useful inmaking the article tolerant to deposition non-uniformity, substratecurvature, substrate sculpting, or substrate shaping which causesshadowing during directional deposition processes, or other geometryfactors that cause a substantially uniform relative shift in all layerthicknesses relative to the typically ideal target thicknesses.

The optical film of one or more embodiments may include or exhibit asensing function or include or exhibit one or more properties enablingsensing. As used herein, sensing may include optical sensing, electricalsensing, magnetic sensing, mechanical sensing or a combination thereof.The sensing function may include capacitive sensing, resistive sensing,inductive sensing, surface acoustic wave sensing, photoelectric sensing,or other known sensing functions. In one or more embodiments, a portionof the optical film (e.g., a single or select layer(s)) may exhibit suchsensing function or one or more properties enabling sensing. In oneembodiment, the optical film or portion thereof may exhibitpiezoelectric properties, pyro-electric properties or a combinationthereof. In some embodiments, the optical film may exhibit piezoelectricproperties but be essentially free of pyro-electric properties and viceversa. One or more piezoelectric layers within the optical film maycomprise crystalline or polycrystalline material, and may also exhibitthe hardness described herein and/or a low optical absorption (and/orhigh optical transparency). In some embodiments, the piezoelectricproperties may be present in one or more aluminum nitride oroxygen-doped aluminum nitride layers within the optical film. In someembodiments, such optical films may sense a magnitude of force orpressure, sense acoustic signals, and/or sense acceleration. Suchembodiments may be described as having an optical film including asensor or sensor layer. The optical film may include or may be used withone or more electrically conducting layers, transparent conductor layers(i.e. optically transparent and electrically conducting layers) and/oroptical waveguiding layers to perform such sensing functions. Theoptical film may be coupled to a signal detector, electrode, or signalprocessor in order to capture, store, or interpret the output of thesensing function.

The articles disclosed herein may include articles with a display (ordisplay articles) (e.g., consumer electronics, including mobile phones,tablets, computers, navigation systems, and the like), architecturalarticles, transportation articles (e.g., automotive, trains, aircraft,sea craft, etc.), appliance articles, or any article that requires sometransparency, scratch-resistance, abrasion resistance or a combinationthereof.

EXAMPLES

Various embodiments will be further clarified by the following examples.Examples 1-9 used modeling to understand the reflectance spectra andcolor shift of articles that included an optical film with an opticalinterference layer, a scratch-resistant layer and a capping layer. Themodeling was based on collected refractive index data from formed layersof various materials and a strengthened aluminoborosilicate (“ABS”)glass substrate. Examples 10, 11, and Comparative Example 12 areexperimentally fabricated multilayer working examples which furtherdemonstrate the principles of modeling Examples 1-9.

The layers were formed by DC reactive sputtering, reactive DC and radiofrequency (RF) sputtering, and e-beam evaporation onto silicon wafers.Some of the formed layers included SiO₂, Nb₂O₅, or Al₂O₃ and weredeposited onto silicon wafers by DC reactive sputtering from a silicon,niobium or aluminum target (respectively) at a temperature of about 50°C. using ion assist. Layers formed in this manner are designated withthe indicator “RS”. Other layers including SiO₂ were deposited ontosilicon wafers by e-beam evaporation by heating the wafer to 300° C. andwithout ion assist. Such layers are designated with the indicator “E”.Layers of Ta₂O₅ were deposited onto silicon wafers by e-beam evaporationby heating the wafer to 300° C. and without ion assist.

Layers of Si_(u)Al_(v)O_(x)N_(y) were deposited onto silicon wafers byDC reactive sputtering combined with RF superimposed DC sputtering, withion assist using a sputter deposition tool supplied by AJA-Industries.The wafer was heated to 200° C. during deposition and silicon targetshaving a 3 inch diameter and an aluminum targets having a 3 inchdiameter were used. Reactive gases used included nitrogen and oxygen andargon was used as the inert gas. The RF power was supplied to thesilicon target at 13.56 Mhz and DC power was supplied to the aluminumtarget. The resulting Si_(u)Al_(v)O_(x)N_(y) layers had a refractiveindex at 550 nm of about 1.95 and a measured hardness of greater thanabout 15 GPa, using a Berkovich indenter on the surface of theSi_(u)Al_(v)O_(x)N_(y) layer being tested, as described herein.

The refractive indices (as a function of wavelength) of the formedlayers of the optical film and the glass substrates were measured usingspectroscopic ellipsometry. Tables 1-7 include the refractive indicesand dispersion curves measured. The refractive indices thus measuredwere then used to calculate reflectance spectra and angular color shiftfor the various modeled Examples.

TABLE 1 Refractive indices and dispersion curve for a RS-SiO2 layer vs.wavelength. Material SiO2-RS Wavelength Refractive Index ExtinctionCoefficient (nm) (n) (k) 246.5 1.52857 0.0 275.2 1.51357 0.0 300.81.50335 0.0 324.7 1.49571 0.0 350.2 1.48911 0.0 375.8 1.48374 0.0 399.71.47956 0.0 425.2 1.47583 0.0 450.7 1.47269 0.0 476.3 1.47002 0.0 500.21.46788 0.0 525.7 1.46589 0.0 549.5 1.46427 0.0 575.0 1.46276 0.0 600.51.46143 0.0 625.9 1.46026 0.0 649.7 1.45928 0.0 675.1 1.45835 0.0 700.51.45751 0.0 725.9 1.45676 0.0 751.3 1.45609 0.0 775.0 1.45551 0.0 800.41.45496 0.0 850.9 1.45399 0.0 899.8 1.45320 0.0 950.2 1.45252 0.0 999.01.45195 0.0 1100.0 1.45100 0.0 1199.6 1.45028 0.0 1302.0 1.44971 0.01400.8 1.44928 0.0 1499.7 1.44892 0.0 1599.0 1.44863 0.0 1688.4 1.448410.0

TABLE 2 Refractive indices and dispersion curve for aSi_(u)Al_(v)O_(x)N_(y) layer vs. wavelength. Material SiAlON-195Wavelength Refractive Index Extinction Coefficient (nm) (n) (k) 206.62.37659 0.21495 225.4 2.28524 0.11270 251.0 2.18818 0.04322 275.52.12017 0.01310 300.9 2.06916 0.00128 324.6 2.03698 0.0 350.2 2.014230.0 360.4 2.00718 0.0 371.2 2.00059 0.0 380.3 1.99562 0.0 389.9 1.990900.0 400.0 1.98640 0.0 410.5 1.98213 0.0 421.7 1.97806 0.0 430.5 1.975130.0 439.7 1.97230 0.0 449.2 1.96958 0.0 459.2 1.96695 0.0 469.6 1.964410.0 480.6 1.96197 0.0 492.0 1.95961 0.0 499.9 1.95808 0.0 512.3 1.955860.0 520.9 1.95442 0.0 529.9 1.95301 0.0 539.1 1.95165 0.0 548.6 1.950310.0 558.5 1.94900 0.0 568.7 1.94773 0.0 579.4 1.94649 0.0 590.4 1.945280.0 601.9 1.94410 0.0 613.8 1.94295 0.0 619.9 1.94239 0.0 632.6 1.941280.0 639.1 1.94074 0.0 652.6 1.93968 0.0 666.6 1.93864 0.0 681.2 1.937630.0 696.5 1.93665 0.0 712.6 1.93569 0.0 729.3 1.93477 0.0 746.9 1.933860.0 765.3 1.93299 0.0 784.7 1.93214 0.0 805.1 1.93131 0.0 826.6 1.930510.0 849.2 1.92973 0.0 873.1 1.92898 0.0 898.4 1.92825 0.0 925.3 1.927540.0 953.7 1.92686 0.0 999.9 1.92587 0.0 1050.7 1.92494 0.0 1107.01.92406 0.0 1169.7 1.92323 0.0 1239.8 1.92245 0.0 1319.0 1.92172 0.01408.9 1.92103 0.0 1512.0 1.92040 0.0 1631.4 1.91981 0.0 1771.2 1.919260.0 1999.8 1.91861 0.0

TABLE 3 Refractive indices and dispersion curve for a strengthenedaluminoborosilicate glass substrate vs. wavelength. Material ABS glassWavelength Refractive Index Extinction Coefficient (nm) (n) (k) 350.61.53119 0.0 360.7 1.52834 0.0 370.8 1.52633 0.0 380.8 1.52438 0.0 390.91.52267 0.0 400.9 1.52135 0.0 411.0 1.52034 0.0 421.0 1.51910 0.0 431.11.51781 0.0 441.1 1.51686 0.0 451.2 1.51600 0.0 461.2 1.51515 0.0 471.21.51431 0.0 481.3 1.51380 0.0 491.3 1.51327 0.0 501.3 1.51259 0.0 511.41.51175 0.0 521.4 1.51124 0.0 531.4 1.51082 0.0 541.5 1.51040 0.0 551.51.50999 0.0 561.5 1.50959 0.0 571.5 1.50918 0.0 581.6 1.50876 0.0 591.61.50844 0.0 601.6 1.50828 0.0 611.6 1.50789 0.0 621.7 1.50747 0.0 631.71.50707 0.0 641.7 1.50667 0.0 651.7 1.50629 0.0 661.7 1.50591 0.0 671.81.50555 0.0 681.8 1.50519 0.0 691.8 1.50482 0.0 701.8 1.50445 0.0 709.81.50449 0.0 719.8 1.50456 0.0 729.9 1.50470 0.0 739.9 1.50484 0.0 749.91.50491 0.0

TABLE 4 Refractive indices and dispersion curve for a RS-Al₂O₃ layer vs.wavelength. Material Al2O3-RS Wavelength Refractive Index ExtinctionCoefficient (nm) (n) (k) 251.3 1.76256 0.0 275.2 1.74075 0.0 300.81.72358 0.0 324.7 1.71136 0.0 350.2 1.70121 0.0 375.8 1.69321 0.0 401.31.68679 0.0 425.2 1.68185 0.0 450.7 1.67747 0.0 474.7 1.67402 0.0 500.21.67089 0.0 525.7 1.66823 0.0 549.5 1.66608 0.0 575.0 1.66408 0.0 600.51.66234 0.0 625.9 1.66082 0.0 649.7 1.65955 0.0 675.1 1.65835 0.0 700.51.65728 0.0 725.9 1.65633 0.0 749.7 1.65552 0.0 775.0 1.65474 0.0 800.41.65404 0.0 850.9 1.65282 0.0 899.8 1.65184 0.0 950.2 1.65098 0.0 999.01.65027 0.0 1100.0 1.64909 0.0 1199.6 1.64821 0.0 1302.0 1.64751 0.01400.8 1.64698 0.0 1499.7 1.64654 0.0 1599.0 1.64619 0.0 1688.4 1.645920.0

TABLE 5 Refractive indices and dispersion curve for an E-Ta₂O₅ layer vs.wavelength. Material Ta2O5-E Wavelength Refractive Index ExtinctionCoefficient (nm) (n) (k) 299.5 2.31978 0.01588 310.0 2.27183 0.00049319.5 2.23697 0.0 329.7 2.20688 0.0 340.6 2.18080 0.0 350.2 2.16164 0.0360.4 2.14448 0.0 369.0 2.13201 0.0 380.3 2.11780 0.0 389.9 2.10741 0.0399.9 2.09780 0.0 410.5 2.08888 0.0 421.7 2.08059 0.0 430.5 2.07475 0.0439.7 2.06920 0.0 449.2 2.06394 0.0 459.2 2.05892 0.0 469.6 2.05415 0.0480.6 2.04960 0.0 488.1 2.04669 0.0 499.9 2.04248 0.0 512.3 2.03846 0.0520.9 2.03588 0.0 529.8 2.03337 0.0 539.1 2.03094 0.0 548.6 2.02857 0.0558.5 2.02627 0.0 568.7 2.02403 0.0 579.4 2.02186 0.0 590.4 2.01974 0.0601.9 2.01768 0.0 613.8 2.01567 0.0 619.9 2.01469 0.0 632.6 2.01276 0.0645.8 2.01088 0.0 659.5 2.00905 0.0 673.8 2.00726 0.0 688.8 2.00552 0.0704.5 2.00382 0.0 729.3 2.00135 0.0 746.9 1.99975 0.0 774.9 1.99743 0.0805.1 1.99518 0.0 826.6 1.99372 0.0 849.2 1.99230 0.0 898.4 1.98955 0.0953.7 1.98692 0.0 999.9 1.98502 0.0 1050.7 1.98318 0.0 1107.0 1.981400.0 1148.0 1.98024 0.0 1192.2 1.97910 0.0 1239.8 1.97799 0.0 1291.51.97690 0.0 1347.7 1.97584 0.0 1408.9 1.97479 0.0 1476.0 1.97376 0.01549.8 1.97276 0.0

TABLE 6 Refractive indices and dispersion curve for an E-SiO₂ layer vs.wavelength. Material SiO2-E Wavelength Refractive Index ExtinctionCoefficient (nm) (n) (k) 299.5 1.48123 0.00296 310.0 1.47856 0.00283319.5 1.47636 0.00273 329.7 1.47424 0.00262 340.6 1.47221 0.00252 350.21.47057 0.00244 360.4 1.46899 0.00236 369.0 1.46776 0.00229 380.31.46628 0.00221 389.9 1.46513 0.00215 399.9 1.46401 0.00209 410.51.46292 0.00203 421.7 1.46187 0.00197 430.5 1.46110 0.00192 439.71.46035 0.00188 449.2 1.45961 0.00183 459.2 1.45890 0.00179 469.61.45820 0.00174 480.6 1.45752 0.00170 488.1 1.45708 0.00167 499.91.45642 0.00163 512.3 1.45579 0.00158 520.9 1.45537 0.00156 529.81.45497 0.00153 539.1 1.45457 0.00150 548.6 1.45418 0.00147 558.51.45379 0.00144 568.7 1.45341 0.00142 579.4 1.45304 0.00139 590.41.45268 0.00136 601.9 1.45233 0.00133 613.8 1.45198 0.00131 619.91.45181 0.00129 632.6 1.45147 0.00126 639.1 1.45130 0.00125 652.51.45098 0.00122 659.5 1.45082 0.00121 673.8 1.45050 0.00118 681.21.45035 0.00117 688.8 1.45019 0.00116 704.5 1.44989 0.00113 720.81.44960 0.00110 746.9 1.44917 0.00106 774.9 1.44876 0.00102 805.11.44836 0.00098 826.6 1.44811 0.00096 849.2 1.44786 0.00093 898.41.44738 0.00088 953.7 1.44693 0.00083 999.9 1.44661 0.00079 1050.71.44631 0.00075 1107.0 1.44602 0.00071 1148.0 1.44584 0.00068 1192.21.44566 0.00066 1239.8 1.44549 0.00063 1291.5 1.44533 0.00061 1347.71.44517 0.00058 1408.9 1.44502 0.00056 1476.0 1.44488 0.00053 1549.81.44474 0.00050

TABLE 7 Refractive indices and dispersion curve for an RS-Nb₂O₅ layervs. wavelength. Material Nb2O5-RS Wavelength Refractive Index ExtinctionCoefficient (nm) (n) (k) 206.6 2.04389 0.66079 250.0 2.32991 1.05691300.2 3.14998 0.45732 325.0 2.94490 0.12012 350.2 2.74715 0.02027 375.12.62064 0.00048 400.6 2.53696 0.0 425.3 2.48169 0.0 450.0 2.44210 0.0475.0 2.41223 0.0 500.9 2.38851 0.0 525.4 2.37086 0.0 549.8 2.35647 0.0575.3 2.34409 0.0 600.4 2.33392 0.0 624.6 2.32557 0.0 650.8 2.31779 0.0675.7 2.31142 0.0 700.5 2.30583 0.0 725.1 2.30093 0.0 749.1 2.29665 0.0774.9 2.29255 0.0 799.9 2.28898 0.0 849.2 2.28288 0.0 901.7 2.27749 0.0999.9 2.26958 0.0 1102.1 2.26342 0.0 1203.7 2.25867 0.0 1298.3 2.255130.0 1400.9 2.25198 0.0 1502.8 2.24939 0.0 1599.8 2.24730 0.0 1698.42.24547 0.0 1796.9 2.24389 0.0 1892.9 2.24254 0.0 1999.7 2.24122 0.02066.4 2.24047 0.0

Example 1

Modeled Example 1 included an article having the same structure as shownin FIG. 6. Modeled Example 1 included a chemically strengthened alkalialuminoborosilicate glass substrate and an optical film disposed on thesubstrate. The optical film included an optical interference layer withthree sets of sub-layers, a scratch-resistant layer disposed on theoptical interference layer and a capping layer disposed on thescratch-resistant layer. The optical film materials and thicknesses ofeach layer, in the order arranged in the optical film, are provided inTable 8.

TABLE 8 Optical film attributes for modeled Example 1. Modeled PhysicalLayer Material Thickness Ambient medium Air Immersed Capping layerRS-SiO₂ 9.5 nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nmOptical 1^(st) low RI sub-layer RS-SiO₂ 8.22 nm inter- 2^(nd) high RIsub-layer Si_(u)Al_(v)O_(x)N_(y) 46.39 nm ference 1^(st) low RIsub-layer RS-SiO₂ 29 nm layer 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 27.87 nm 1^(st) low RI sub-layer RS-SiO₂ 49.63 nm2^(nd) high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 9.34 nm Substrate ABSGlass Immersed

The calculated reflectance spectrum for modeled Example 1 is shown inFIG. 7. As shown in FIG. 7, the oscillations in the reflectance spectrumare small (i.e., less than about 0.5 percentage points over the opticalwavelength regime), leading to relatively low calculated visible colorshift for a 10 degree observer, over a range of incidence viewing anglesfrom 60 degrees to normal incidence, under an F2 illuminant, as shown inFIG. 8. FIG. 7 shows a target having a radius of 0.2, centered on thecolor coordinates of the substrate without the optical film disposedthereon, under F2 illumination.

Example 2

Modeled Example 2 included an article 200 with a chemically strengthenedalkali aluminoborosilicate substrate 210 and an optical film 220disposed on the substrate. The optical film 220 included an opticalinterference layer 230, a scratch-resistant layer 240 disposed on theoptical interference layer, and a capping layer 250, as shown in FIG. 9.The optical interference layer 230 included four sets of sub-layers231A, 231B. The optical film materials and thicknesses of each layer, inthe order arranged in the optical film, are provided in Table 9.

TABLE 9 Optical film attributes for modeled Example 2. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer RS-SiO₂ 9.5nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nm Optical 1^(st)low RI sub-layer RS-SiO₂ 4.83 nm inter- 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 53.16 nm ference 1^(st) low RI sub-layer RS-SiO₂19.63 nm layer 2^(nd) high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 38.29 nm1^(st) low RI sub-layer RS-SiO₂ 40.97 nm 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 21.73 nm 1^(st) low RI sub-layer RS-SiO₂ 54.88 nm2^(nd) high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 7.05 nm Substrate ABSGlass Immersed

The calculated reflectance spectrum for the modeled Example 2 is shownin FIG. 10. As shown in FIG. 10, the oscillations in the reflectancespectrum are small (i.e., less than about 0.5 percentage points over theoptical wavelength regime), leading to relatively low calculated visiblecolor shift for a 10 degree observer, over a range of incidence viewingangles from 60 degrees to normal incidence, under an F2 illuminant, asshown in FIG. 11. FIG. 11 shows a target having a radius of 0.2,centered on the color coordinates of the substrate without the opticalfilm disposed thereon, under F2 illumination.

Example 3

Modeled Example 3 included an article 300 with a chemically strengthenedalkali aluminoborosilicate substrate 310 and an optical film 320disposed on the substrate. The optical film 320 included an opticalinterference layer 330, a scratch resistant layer 340 disposed on theoptical interference layer, and a capping layer 350 disposed on thescratch-resistant layer 250. The optical interference layer included twosets of sub-layers 331A, 331B, a third sub-layer 331C disposed betweenthe plurality of sub-layers and the scratch-resistant layer, and a thirdsub-layer 331D disposed between the plurality of sub-layers and thesubstrate, as shown in FIG. 12. The optical film materials andthicknesses of each layer, in the order arranged in the optical film,are provided in Table 10.

TABLE 10 Optical film attributes for modeled Example 3. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer RS-SiO₂ 9.5nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nm Optical Thirdsub-layer RS-Al₂O₃ 13.5 nm inter- 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 43.58 nm ference 1^(st) low RI sub-layer RS-SiO₂28.85 nm layer 2^(nd) high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 27.48 nm1^(st) low RI sub-layer RS-SiO₂ 40.62 nm Third sub-layer RS-Al₂O₃ 27.26nm Substrate ABS Glass Immersed

The calculated reflectance spectrum for the modeled Example 3 is shownin FIG. 13. As shown in FIG. 13, the oscillations in the reflectancespectrum are small (i.e., less than about 0.5 percentage points over theoptical wavelength regime), leading to relatively low calculated visiblecolor shift for a 10 degree observer, over a range of incidence viewingangles from 60 degrees to normal incidence, under an F2 illuminant, asshown in FIG. 14. FIG. 14 shows a target having a radius of 0.2,centered on the color coordinates of the substrate without the opticalfilm disposed thereon, under F2 illumination.

Example 4

Modeled Example 4 included an article 400 with a chemically strengthenedalkali aluminoborosilicate substrate 410 and an optical film 420disposed on the substrate. The optical film 420 included an opticalinterference layer 430, a scratch resistant layer 440 disposed on theoptical interference layer, and a capping layer 450 disposed on thescratch-resistant layer. The optical interference layer included threesets of sub-layers 431A, 431B, a third sub-layer 431C disposed betweenthe plurality of sub-layers and the scratch-resistant layer, and a thirdsub-layer 431D disposed between the plurality of sub-layers and thesubstrate, as shown in FIG. 15. The optical film materials andthicknesses of each layer, in the order arranged in the optical film,are provided in Table 11.

TABLE 11 Optical film attributes for modeled Example 4. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer RS-SiO₂ 9.5nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nm Optical Thirdsub-layer RS-Al₂O₃ 10.20 nm inter- 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 49.01 nm ference 1^(st) low RI sub-layer RS-SiO₂23.30 nm layer 2^(nd) high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 35.04 nm1^(st) low RI sub-layer RS-SiO₂ 44.95 nm 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 19.02 nm 1^(st) low RI sub-layer RS-SiO₂ 50.45 nmThird sub-layer RS-Al₂O₃ 17.16 nm Substrate ABS Glass Immersed

The calculated reflectance spectrum for the modeled Example 4 is shownin FIG. 16. As shown in FIG. 16, the oscillations in the reflectancespectrum are small (i.e., less than about 0.5 percentage points over theoptical wavelength regime), leading to relatively low calculated visiblecolor shift for a 10 degree observer, over a range of incidence viewingangles from 60 degrees to normal incidence, under an F2 illuminant, asshown in FIG. 17. FIG. 17 shows a target having a radius of 0.2,centered on the color coordinates of the substrate without the opticalfilm disposed thereon, under F2 illumination.

Example 5

Modeled Example 5 included an article 500 with a chemically strengthenedalkali aluminoborosilicate substrate 510 and an optical film 520disposed on the substrate. The optical film 520 included an opticalinterference layer 530, a scratch resistant layer 540 disposed on theoptical interference layer, and a capping layer 550 disposed on thescratch-resistant layer 550. The optical interference layer included sixsets of sub-layers 531A, 531B and a third sub-layer 531C disposedbetween the plurality of sub-layers and the scratch-resistant layer, asshown in FIG. 18. The optical film materials and thicknesses of eachlayer, in the order arranged in the optical film, are provided in Table12.

TABLE 12 Optical film attributes for modeled Example 5. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer RS-SiO₂ 14nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nm Optical Thirdsub-layer RS-Al₂O₃ 7.05 nm inter- 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 54.65 nm ference 1^(st) low RI sub-layer RS-Al₂O₃24.59 nm layer 2^(nd) high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 37.96 nm1^(st) low RI sub-layer RS-Al₂O₃ 52.53 nm 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 17.48 nm 1^(st) low RI sub-layer RS-Al₂O₃ 90.07nm 2^(nd) high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 20.63 nm 1^(st) lowRI sub-layer RS-Al₂O₃ 38.15 nm 2^(nd) high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 84.11 nm 1^(st) low RI sub-layer RS-Al₂O₃ 6.87 nm2^(nd) high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 48.85 nm 1^(st) low RIsub-layer RS-Al₂O₃ 81.63 nm Substrate ABS Glass Immersed

The calculated reflectance spectrum for the modeled Example 5 is shownin FIG. 19. As shown in FIG. 19, the oscillations in the reflectancespectrum are small (i.e., less than about 1 percentage point over theoptical wavelength regime), which would lead to a relatively low visiblecolor shift when viewed at an incidence viewing angle in the range fromabout 0 degrees to about 60 degrees to normal incidence, under anilluminant.

Example 6

Modeled Example 6 included an article 600 with a chemically strengthenedalkali aluminoborosilicate substrate 610 and an optical film 620disposed on the substrate. The optical film 620 included an opticalinterference layer 630, a scratch resistant layer 640 disposed on theoptical interference layer, and a capping layer 650 disposed on thescratch-resistant layer 650. The optical interference layer included twosets of sub-layers 631A, 631B and a third sub-layer 631C disposedbetween the plurality of sub-layers and the substrate, as shown in FIG.20. The optical film materials and thicknesses of each layer, in theorder arranged in the optical film, are provided in Table 13.

TABLE 13 Optical film attributes for modeled Example 6. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer RS-SiO₂ 10nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nm Optical 2^(nd)high RI sub-layer E-Ta₂O₅ 15.27 nm inter- 1^(st) low RI sub-layer E-SiO₂19.35 nm ference 2^(nd) high RI sub-layer E-Ta₂O₅ 32.53 nm layer 1^(st)low RI sub-layer E-SiO₂ 43.18 nm Third sub-layer E-Ta₂O₅ 12.64 nmSubstrate ABS Glass Immersed

The calculated reflectance spectrum for the modeled Example 6 is shownin FIG. 21. As shown in FIG. 21, the oscillations in the reflectancespectrum are small (i.e., less than about 1 percentage point over theoptical wavelength regime), leading to relatively low calculated visiblecolor shift for a 10 degree observer, over a range of incidence viewingangles from 60 degrees to normal incidence, under an F2 illuminant, asshown in FIG. 26. FIG. 26 shows a target having a radius of 0.2,centered on the color coordinates of the substrate without the opticalfilm disposed thereon, under F2 illumination.

Example 7

Modeled Example 7 included an article 700 with a chemically strengthenedalkali aluminoborosilicate substrate 710 and an optical film 720disposed on the substrate. The optical film 720 included an opticalinterference layer 730, a scratch resistant layer 740 disposed on theoptical interference layer, and a capping layer 750 disposed on thescratch-resistant layer 750. The optical interference layer includedthree sets of sub-layers 731A, 731B, and a third sub-layer 731C betweenthe plurality of sub-layers and the substrate, as shown in FIG. 22. Theoptical film materials and thicknesses of each layer, in the orderarranged in the optical film, are provided in Table 14.

TABLE 14 Optical film attributes for modeled Example 7. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer RS-SiO₂ 10nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nm Optical 2^(nd)high RI sub-layer E-Ta₂O₅ 18.67 nm inter- 1^(st) low RI sub-layer E-SiO₂13.7 nm ference 2^(nd) high RI sub-layer E-Ta₂O₅ 39.23 nm layer 1^(st)low RI sub-layer E-SiO₂ 32.77 nm 2^(nd) high RI sub-layer E-Ta₂O₅ 24.91nm 1^(st) low RI sub-layer E-SiO₂ 50.89 nm Third sub-layer E-Ta₂O₅ 8.39nm Substrate ABS Glass Immersed

The calculated reflectance spectrum for the modeled Example 7 is shownin FIG. 22. As shown in FIG. 22, the oscillations in the reflectancespectrum are small (i.e., less than about 0.5 percentage points over theoptical wavelength regime and, in some cases, less than about 0.1percentage points over the optical wavelength regime), leading torelatively low calculated visible color shift for a 10 degree observer,over a range of incidence viewing angles from 60 degrees to normalincidence, under an F2 illuminant, as shown in FIG. 26.

Example 8

Modeled Example 8 included an article 800 with a chemically strengthenedalkali aluminoborosilicate substrate 810 and an optical film 820disposed on the substrate. The optical film 820 included an opticalinterference layer 830, a scratch resistant layer 840 disposed on theoptical interference layer, and a capping layer 850 disposed on thescratch-resistant layer 840. The optical interference layer includedfour sets of sub-layers 831A, 831B, and a third sub-layer 831C disposedbetween the plurality of sub-layers and the scratch-resistant layer, asshown in FIG. 23. The optical film materials and thicknesses of eachlayer, in the order arranged in the optical film, are provided in Table15.

TABLE 15 Optical film attributes for modeled Example 8. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer RS-SiO₂ 10nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nm Optical Thirdsub-layer E-Ta₂O₅ 19.52 nm inter- 1^(st) low RI sub-layer E-SiO₂ 11.28nm ference 2^(nd) high RI sub-layer E-Ta₂O₅ 44.68 nm layer 1^(st) low RIsub-layer E-SiO₂ 25.72 nm 2^(nd) high RI sub-layer E-Ta₂O₅ 34.69 nm1^(st) low RI sub-layer E-SiO₂ 45.76 nm 2^(nd) high RI sub-layer E-Ta₂O₅20.24 nm 1^(st) low RI sub-layer E-SiO₂ 57.29 nm 2^(nd) high sub-layerE-Ta₂O₅ 6.64 nm Substrate ABS Glass Immersed

The calculated reflectance spectrum for the modeled Example 8 is shownin FIG. 25. As shown in FIG. 25, the oscillations in the reflectancespectrum are small (i.e., less than about 0.25 percentage points overthe optical wavelength regime and, in some cases, less than about 0.1percentage points over the optical wavelength regime), leading torelatively low calculated visible color shift for a 10 degree observer,over a range of incidence viewing angles from 60 degrees to normalincidence, under an F2 illuminant, as shown in FIG. 26.

Example 9

Modeled Example 9 included an article 900 with a chemically strengthenedalkali aluminoborosilicate substrate 910 and an optical film 920disposed on the substrate. The optical film 920 included an opticalinterference layer 930, a scratch resistant layer 940 disposed on theoptical interference layer, and a capping layer 950 disposed on thescratch-resistant layer 950. The optical interference layer includedthree sets of sub-layers 931A, 931B, and a third sub-layer 931C betweenthe plurality of sub-layers and the scratch-resistant layer, as shown inFIG. 27. The optical film materials and thicknesses of each layer, inthe order arranged in the optical film, are provided in Table 16.

TABLE 16 Optical film attributes for modeled Example 9. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer RS-SiO₂ 14nm Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 2000 nm Optical Thirdsub-layer RS-Nb₂O₅ 7.0 nm inter- 1^(st) low RI sub-layer RS-SiO₂ 23.02nm ference 2^(nd) high RI sub-layer RS-Nb₂O₅ 19.75 nm layer 1^(st) lowRI sub-layer RS-SiO₂ 41.60 nm 2^(nd) high RI sub-layer RS-Nb₂O₅ 14.68 nm1^(st) low RI sub-layer RS-SiO₂ 57.14 nm 2^(nd) high sub-layer RS-Nb₂O₅5.08 nm Substrate ABS Glass Immersed

The calculated reflectance spectrum for the modeled Example 9 is shownin FIG. 28. As shown in FIG. 28, the oscillations in the reflectancespectrum are small (i.e., less than about 1 percentage points over theoptical wavelength regime and, in some cases, less than about 0.1percentage points over the optical wavelength regime), which would leadto a relatively low visible color shift at an incidence viewing angle inthe range from about 0 degrees to about 60 degrees to normal incidence,under an illuminant.

Examples 10-11 and Comparative Example 12

Example 10 was made and included a substrate, and an optical filmdisposed on the substrate. The substrate included a chemicallystrengthened ABS glass substrate having a compressive stress of about900 MPa and a DOL of about 45 μm. As shown in Table 17, the optical filmincluded an optical interference layer with six sub-layer sets. The sixsub-layer sets included first low RI sub-layer of SiOxNy (having arefractive index value of about 1.49 at a wavelength of about 550 nm)and a second high RI sub-layer of AlO_(x)N_(y) (having a refractiveindex value of about 2.0 at a wavelength of about 550 nm). The opticalfilm also included an AlO_(x)N_(y) scratch resistant layer. The opticalinterference layer of Example 10 was formed using reactive magnetronsputtering using an AJA-Industries sputter deposition tool usingoxidizing and nitridizing environments. Sputter targets used included a3″ diameter silicon target and a 3″ diameter aluminum target.

The first low RI layer was formed by supplying about 490 W RF to thesilicon target. During formation of the first low RI layer, about 75 WRF and 50 W DC were supplied to the aluminum target; however, thealuminum shutter was closed to prevent deposition of aluminum. Duringdeposition of the first low RI sub-layers, oxygen was flowed into thereactor at a flow rate of about 3.3 sccm, argon was flowed into thereactor at a flow rate of about 30 sccm and nitrogen gas was flowed intothe reactor at a flow rate of about 30 sccm. The deposition times forthe first low RI sub-layers were modified to provide the thicknessesshown in Tables 17 and 18.

The second high RI sub-layers were disposed using RF superimposed DCpower directed at the aluminum target. About 300 W of DC power wassupplied to the aluminum target and about 200 W of RF power was suppliedto the Al target. During formation of the second high RI layer, RF powerwas supplied to the silicon target at about 50 W; however, the siliconshutter was closed to prevent deposition of silicon. During depositionof the second high RI sub-layers, oxygen was flowed into the reactor ata flow rate of 0.25 sccm, argon was flowed into the reactor at a flowrate of about 30 sccm and nitrogen gas was flowed into the rector at arate of about 30 sccm. The deposition times for the second high RIsub-layers were modified to provide the thicknesses shown in Tables 17and 18.

Table 17 also provides the refractive index values for the respectivefirst low RI sub-layers, second high RI sub-layers and thescratch-resistant layer, at a wavelength of about 550 nm. The entiredispersion curves for these sub-layers are similar to analogousmaterials used in Modeled Examples 1-9 (whose refractive indexdispersions were also measured experimentally). Dispersion curves usedin Modeled Examples 1-9 can be shifted up or down slightly by a linearor scaled amount at each wavelength to arrive at the target refractiveindices used in Examples 10 and 11 to very closely reproduce the actualdispersion curves of the materials in working Examples 10 and 11.

At each of the transitions between the first low RI sub-layers (SiOxNy)and the second high RI sub-layers (AlOxNy), both the silicon andaluminum shutters were closed for about 60 seconds, as the gas flowswere transitioned to those required for the following sub-layer. Duringthis transition, the powers and gas flows were adjusted. The sputteringwas maintained “on” but the sputtered material went onto the closedshutter. The power supplied to the silicon target was left at about 500W in some cases to scavenge remnant oxygen, since the second high RIsub-layer utilized a low oxygen flow (as compared to the oxygen flowused to form the first low RI sub-layer). This process allowed thesputter targets to attain their desired powers, in the presence of thegases that were used for the various layers, prior to opening theshutters for a given sub-layer.

The scratch-resistant layer was formed using the same conditions as usedto form the second high RI sub-layers. The resulting scratch-resistantlayer combined with the optical interference layers as describedexhibited a hardness of about 15 GPa, as measured using a Berkovichindenter as described herein and a modulus of about 212 GPa as measuredby known nanoindentation methods.

TABLE 17 Optical film target refractive indices and thicknesses forExample 10. Target Target Refractive Index Thickness Layer Material @550nm (nm) Scratch-resistant layer AlO_(x)N_(y) 2.00709 2000 First low RIsub-layer SiO_(x)N_(y) 1.49658 9.7 Second high RI sub-layer AlO_(x)N_(y)2.00709 42.17 First low RI sub-layer SiO_(x)N_(y) 1.49658 30.27 Secondhigh RI sub-layer AlO_(x)N_(y) 2.00709 24.68 First low RI sub-layerSiO_(x)N_(y) 1.49658 52.71 Second high RI sub-layer AlO_(x)N_(y) 2.007098.25 Substrate ABS glass 1.51005

TABLE 18 Sputtering process conditions used for Example 10. Sputter TimeSi W Si Al W Al W Al O₂ Ar N₂ Layer Material (sec) RF shutter RF DCshutter flow flow flow Scratch-resistant AlO_(x)N_(y) 32756.6 50 closed200 300 open 3.3 30 30 layer First low RI sub- SiO_(x)N_(y) 121.9 490open 75 50 closed 0.25 30 30 layer Second high RI AlO_(x)N_(y) 710.3 50closed 200 300 open 3.3 30 30 sub-layer First low RI sub- SiO_(x)N_(y)448.3 490 open 75 50 closed 0.25 30 30 layer Second high RI AlO_(x)N_(y)440.6 50 closed 200 300 open 3.3 30 30 sub-layer First low RI sub-SiO_(x)N_(y) 804.2 490 open 75 50 closed 0.25 30 30 layer Second high RIAlO_(x)N_(y) 104.3 50 closed 200 300 open 3.3 30 30 sub-layer SubstrateABS glass Total Time: 35523.0

Example 11 was formed using the same equipment and similar reactivesputtering processes as Example 10; however Example 11 includedSi_(u)Al_(c)O_(x)N_(y) in the second high RI sub-layers and as thescratch resistant layer, which had a refractive index at a wavelength ofabout 550 nm of about 1.998. The same substrate was used in Example 11as was used in Example 10. The optical film design for Example 11 andsputtering process conditions used to form Example 11 are shown inTables 19 and 20.

Example 11 was measured for hardness using a Berkovich diamond indenterand an indentation depth of about 100 nm, as described herein, and thearticle of Exhibit 11 had a measured hardness of 21 GPa. Example 11 alsoexhibited an elastic modulus of 237 GPa.

TABLE 19 Optical film target refractive indices and thicknesses forExample 11. Target Target Refractive Index Thickness Layer Material @550nm (nm) Scratch-resistant layer Si_(u)Al_(v)O_(x)N_(y) 1.99823 2000First low RI sub-layer SiO_(x)N_(y) 1.49594 11.8 Second high RIsub-layer Si_(u)Al_(v)O_(x)N_(y) 1.99823 45.4 First low RI sub-layerSiO_(x)N_(y) 1.49594 33.6 Second high RI sub-layerSi_(u)Al_(v)O_(x)N_(y) 1.99823 27.5 First low RI sub-layer SiO_(x)N_(y)1.49594 56.5 Second high RI sub-layer Si_(u)Al_(v)O_(x)N_(y) 1.9982310.1 Substrate ABS glass 1.51005

TABLE 20 Sputtering process conditions for Example 11. Sputter Si W SiAl W Al W Al O2 Ar N2 Layer Material Time (sec) RF shutter RF DC shutterflow flow flow Scratch-resistant Si_(u)Al_(v)O_(x)N_(y) 18340.0 500 open200 300 open 3.3 30 30 layer First low RI SiO_(x)N_(y) 135.0 500 open 5050 closed 0.5 30 30 sub-layer Second high RI Si_(u)Al_(v)O_(x)N_(y)440.0 500 open 200 300 open 3.3 30 30 sub-layer First low RISiO_(x)N_(y) 385.0 500 open 50 50 closed 0.5 30 30 sub-layer Second highRI Si_(u)Al_(v)O_(x)N_(y) 275.0 500 open 200 300 open 3.3 30 30sub-layer First low RI SiO_(x)N_(y) 640.0 500 open 50 50 closed 0.5 3030 sub-layer Second high RI Si_(u)Al_(v)O_(x)N_(y) 195.0 500 open 200300 open 3.3 30 30 sub-layer Substrate ABS glass Total time: 20410.0

Comparative Example 12 was formed using the same substrate as Examples10 and 11, but film disposed on the substrate was formed by reactivesputtering using a Shincron rotary drum coater. The film of ComparativeExample 12 included a single optical interference layer disposed betweena scratch-resistant layer and the glass substrate. Comparative Example12 included the following structure: glass substrate/115 nm opticalinterference layer of Al₂O₃/2000 nm scratch-resistant layer ofAlO_(x)N_(y)/32 nm capping layer of SiO₂.

The optical properties of Examples 10 and 11 and Comparative Example 12are summarized in FIGS. 29-31. FIG. 29 shows the transmittance spectrafor Examples 10-11 and Comparative Example 12. FIG. 30 shows themeasured reflected light color coordinates for Examples 10-11 with F2illumination at different incident illumination angles (e.g., 5, 20, 40,and 60 degrees). FIG. 31 shows the measured transmitted light colorcoordinates for Examples 10-11 with D65 illumination at an incidentillumination angle of 5 degrees. Circular target lines are shown inFIGS. 30 and 31 as guides for the eye.

The oscillation amplitudes in transmittance for Example 10 was measuredas less than about 3 percentage points for any 50 nm or 100 nmwavelength range segment, within the broader wavelength range from about450 nm to about 650 nm, or from about 400 nm to about 700 nm. As shownin FIG. 30, the maximum variation in reflected color coordinates forExample 10 under F2 illumination with measurement incident illuminationangle varying from 5 to 60 degrees was less than +/−1.5 in b* colorcoordinate and less than +/−0.5 in a* color coordinate. As shown in FIG.31, the transmitted color coordinates for Example 10 under D65illumination at 5 degree incident illumination angle varies from theuncoated glass color coordinates by less than +/−0.2 in b* colorcoordinate and less than +/−0.1 in a* color coordinate.

The oscillation amplitudes in transmittance for Example 11 was measuredas less than about 3 percentage points for any 50 nm or 100 nmwavelength range segment, within the broader wavelength range from about450 nm to about 650 nm, or from about 400 nm to about 700 nm. In someinstances, the oscillation amplitude was even less than 2 percentagepoints from some 50 nm or 100 nm wavelength range segments. As shown inFIG. 30, the maximum variation in reflected color coordinates forExample 11 under F2 illumination with measurement incident illuminationangle varying from 5 to 60 degrees is less than +/−0.4 in both a* and b*color coordinates. As shown in FIG. 31, the transmitted colorcoordinates for Example 11 under D65 illumination at 5 degrees variesfrom the uncoated glass color coordinates by less than +/−0.4 in b*color coordinate and less than +/−0.1 in a* color coordinate.

The oscillation amplitudes in transmittance for Comparative Example 12were comparatively large, as shown in FIG. 29. From this data, it can bepredicted that the color coordinates a* and b* would vary substantiallyunder the same illuminants and the same incident illumination angles asused to evaluate Examples 10 and 11.

The absolute color coordinates for Examples 10 and 11 could be furthertuned by adding a capping layer (e.g., a capping layer having athickness in the range from about 5 nm to about 25 nm of SiO₂ orSiO_(x)N_(y)), as shown in the modeled Examples. The range of colorvariation and reflectance/transmittance oscillations seen in Examples 10and 11 is in a low and useful range, although the color variation issomewhat larger than that seen in the modeled Examples. This differencebetween the modeled Examples 1-9 and Examples 10-11 is believed to be afunction of layer thickness and index variations encountered during thereactive RF sputtering process. There are a variety of methods known inthe art for forming the optical films of Examples 10-11 and describedherein, which were not used in these experiments, which could furtherimprove the control of the experimentally fabricated layer and sub-layerthicknesses and refractive indices. Exemplary methods include slowerdeposition rates for the thinnest layers in the optical film, optical orquartz crystal thickness monitoring of layer or sub-layer thicknessduring deposition, plasma emission or mass spectrometric monitoring ofthe gas composition in the chamber during deposition; and other knowntechniques used to control layer thickness and composition in thin filmdeposition.

The optical interference layers used in the Examples were designed tominimize reflection between the scratch-resistant layer and thesubstrate, thus reducing reflectance oscillation for the entire article.The reduced reflectance oscillation (or reflectance oscillations havingreduced amplitudes), provided low observed color and low color shifts atdifferent incidence viewing angles under multiple illumination sources,including illumination sources with sharp wavelength spikes such as CIEF2 and F10 illumination. The scratch-resistant layer exhibited ahardness of greater than about 15 GPa when measured using a Berkovichindenter, as described herein, and in some cases even greater than 20GPa.

Example 13

Modeled Example 13 included an article 1000 with a chemicallystrengthened glass substrate 1010 and an optical film 1020 disposed onthe substrate. The optical film 1020 included an optical interferencelayer 1030, a scratch resistant layer 1040 disposed on the opticalinterference layer, and a capping layer 1050 disposed on thescratch-resistant layer 1040. The optical interference layer includedthree sets of sub-layers 1031A, 1031B, between the substrate and thescratch-resistant layer, as shown in FIG. 32. The optical film materialsand thicknesses of each layer, in the order arranged in the opticalfilm, are provided in Table 21.

TABLE 21 Optical film attributes for modeled Example 13. Layer MaterialModeled Thickness Ambient medium Air Immersed Capping layer SiO₂ 10 nmScratch-resistant layer AlOxNy 2000 nm Optical 1^(st) low RI sub-layerSiO₂ 10 nm inter- 2^(nd) high RI sub-layer AlOxNy 50 nm ference 1^(st)low RI sub-layer SiO₂ 25 nm layer 2^(nd) high RI sub-layer AlOxNy 25 nm1^(st) low RI sub-layer SiO₂ 50 nm 2^(nd) high sub-layer AlOxNy 10 nmSubstrate ABS Glass Immersed

Example 13 has symmetrical optical interference layer. In one or moreembodiments, the optical interference layer may be modified to havedifferent sub-layers and sub-layers with different thicknesses so longas the symmetry is preserved.

Example 14

Example 14A was formed using an aluminosilicate glass substrate that waschemically strengthened and exhibited a compressive stress in the rangefrom about 700 MPa to about 900 MPa and a depth of compressive stresslayer in the range from about 40 about 40 μm to about 50 μm. Example 14Aincluded an optical film including the following structure shown inTable 22, with the thickness of each layer varying by no more than 5 nm,due to manufacturing tolerances.

TABLE 22 Optical Film Attributes of Example 14A. Layer MaterialThickness Capping layer SiO₂ 10 nm Scratch-resistant layer AlOxNy 2000nm Optical 1^(st) low RI sub-layer SiO₂ 10 nm inter- 2^(nd) high RIsub-layer AlOxNy 50 nm ference 1^(st) low RI sub-layer SiO₂ 30 nm layer2^(nd) high RI sub-layer AlOxNy 30 nm 1^(st) low RI sub-layer SiO₂ 50 nm2^(nd) high sub-layer AlOxNy 10 nm

Comparative Example 14B included the same substrate as Example 14A butwas uncoated. Comparative Example 14C included the same substrate asExample 14A with a hydrophobic, low-friction fluorosilane coating havinga thickness of about 10 nm disposed on the substrate. ComparativeExamples 14D-14F included the same substrate as Example 14A with asingle layer of either Si_(u)Al_(v)O_(x)N_(y) having a thickness of 186nm (14D) or 478 nm (14E) or AlO_(x)N_(y) with a thickness of about 294nm (14F).

The coatings on Example 14A, and Comparative Examples 14D-14F wereformed using reactive DC sputtering or combined reactive DC and RFsputtering from metallic targets. It should be noted that layers ofAlO_(x)N_(y) can often be substituted for the layers ofSi_(u)Al_(v)O_(x)N_(y) layers and can be formed using the same or asimilar process used to form such layers. Both Si_(u)Al_(v)O_(x)N_(y),and AlO_(x)N_(y) layers can be made which exhibited a refractive indexat 550 nm of about 1.95-2.05 and a measured hardness greater than 15 GPameasured using the Berkovich Indentation Hardness Test along anindentation depth of about 100 nm or greater.

Table 23 shows scattered light intensity (CCBTDF, 1/steradian) andtransmission haze (with 8 mm aperture) after subjecting the samples tothe Taber Test. Table 23 also shows the average scattered lightintensity value and haze value of Example 14A, and Comparative Examples14B-F, as a baseline. Lower scattered light intensity and lower hazecorrelates to less visible scratches and less visible damage after theabrasion test. Example 14A exhibited the lowest scattered lightintensity and haze after the Taber Test indicating superior resistanceto multiple contact event damage.

TABLE 23 Scattered Light Intensity and Haze Measurements for Example 14Aand Comparative Examples 14B-14F. Scattered light Range of intensity -Avg. +/− Transmis- Std. Dev. (CCBTDF, sion Haze 1/steradian) With 8 mmExamples At 20 degrees aperture Comparative Example 14B - IX 0.021 +/−0.004 0.1-0.4 glass (no coating) Comparative Example 14C - IX 0.022 +/−0.015 0.25-0.35 Glass + hydrophobic, low- friction fluorosilane coatingComp. Ex. 14D - IX Glass + 1 L 0.03 +/− 0.01 0.8 SiuAlvOxNy 186 nm Comp.Ex. 14E - IX Glass + 1 L 0.018 +/− 0.001 0.3 SiuAlvOxNy 478 nm Comp. Ex.14F - IX Glass + 1 L 0.174 +/− 0.04  5.1 AlOxNy 294 nm Example 14A 3 LSRC Al₂O₃/  0.002 +/− 0.0001  0.05 AlON/SiO₂ Average of non-abradedregions 0.002 +/− 0.001   0-0.2 of Examples 14A and Compara- tiveExamples 14B-12F

Example 14A was also subjected to the Garnet Test (separately from theTaber Test) at different total loads, as shown in Table 24. ComparativeExample 14B was also subjected to the Garnet Test (separately from theTaber Test) for comparison.

TABLE 24 Garnet Test results of Example 14A and Comparative Example 14B.Scattered light at Haze (with 8 mm aperture) after Garnet 20 degreesTotal Load Test with specified total load (g) (CCBTDF, 1/sr) applied 380g 500 g 750 g 1500 g 2100 g 2100 g Comparative 0.4 0.5 1.2 3.2 3.5 0.053+/− 0.03  Ex. 14B Example 0 0 0 0 0.1 0.002 +/− 0.0005 14A

As shown in Table 24, Example 14A exhibited significantly less haze andless scattered light after the Garnet Test at all loads as compared toComparative Example 14B.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the invention.

What is claimed is:
 1. A device comprising: a cover article, the coverarticle comprising a substrate having a surface, and an optical filmdisposed on the substrate surface forming a coated surface, the opticalfilm comprising a scratch-resistant layer and an optical interferencelayer disposed between the scratch-resistant layer and the substrate,the optical interference layer comprises a physical thickness of about800 nm, wherein the cover article comprises a maximum hardness of 8 GPaor greater, as measured by a Berkovich Indenter Hardness Test alongindentation depths of about 100 nm or greater, and a color shift of 2 orless, when viewed at an incident illumination angle in the range fromabout 2 degrees to about 60 degrees from normal incidence under anilluminant comprising CIE A illuminants, CIE B illuminants CIE Cilluminants, CIE D illuminants or CIE F illuminants, and further whereincolor shift is determined by the equation √((a*₂−a*₁)₂+(b*₂+b*₁)²),where a*₁ and b*₁ are coordinates of the article when viewed at normalincidence and a*₂, and b*₂ are coordinates of the article viewed at theincident illumination angle, and wherein the coordinates of the articlewhen viewed at normal incidence and at the incident illumination angleare both in transmittance or reflectance.
 2. The device of claim 1,wherein the optical interference layer comprises a physical thicknessfrom about 10 nm to about 500 nm.
 3. The device of claim 1, wherein theoptical interference layer comprises a physical thickness from about 10nm to about 450 nm.
 4. The device of claim 1, wherein the opticalinterference layer comprises a physical thickness from about 50 nm toabout 300 nm.
 5. The device of claim 1, wherein the cover articlecomprises a maximum hardness of 10 GPa or greater, as measured by aBerkovich Indenter Hardness Test along indentation depths of about 100nm or greater.
 6. The device of claim 1, wherein the opticalinterference layer comprises a maximum hardness in the range of about 6GPa to about 30 GPa, as measured by a Berkovich Indenter Hardness Testalong indentation depths of about 50 nm or greater.
 7. The device ofclaim 1, wherein the optical interference layer comprises a plurality ofsub-layer sets, the plurality of sub-layer sets comprising a first lowrefractive index (RI) sub-layer and a second high refractive index (RI)sub-layer.
 8. The device of claim 7, wherein the difference between therefractive index of the first low RI sub-layer and the refractive indexof the second high RI sub-layer is about 0.01 or greater.
 9. The deviceof claim 7, wherein the first low RI sub-layer comprises asilicon-containing oxide, the second RI sub-layer comprises asilicon-containing nitride, and the scratch resistant layer comprises asilicon-containing oxide.
 10. The device of claim 7, wherein: the firstlow RI sub-layer comprises at least one of SiO₂, Al₂O₃, GeO₂, SiO,AlO_(x)N_(y), SiO_(x)N_(y), Si_(u)Al_(v)O_(x)N_(y), MgO, MgF₂, BaF₂,CaF₂, DyF₃, YbF₃, YF₃, and CeF₃, and the second high RI sub-layercomprises at least one of Si_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, Si₃N₄,AlO_(x)N_(y), SiO_(x)N_(y), HfO₂, TiO₂, ZrO₂, Y₂O₃, Al₂O₃, and MoO₃. 11.The device of claim 7, wherein at least one of the first low RIsub-layer and the second high RI sub-layer comprises an opticalthickness (n*d) in the range from about 2 nm to about 200 nm.
 12. Thedevice of claim 1, wherein the optical interference layer comprises anaverage light reflection of about 2% or less over the optical wavelengthregime.
 13. The device of claim 1, wherein the substrate comprises aglass selected from the group consisting of soda lime glass, alkalialuminosilicate glass, alkali containing borosilicate glass and alkalialuminoborosilicate glass.
 14. The device of claim 1, wherein thesubstrate comprises a glass that is chemically strengthened andcomprises a compressive stress (CS) layer with a surface CS of at least250 MPa extending within the chemically strengthened glass from asurface of the chemically strengthened glass to a depth of layer (DOL)of at least about 10 μm.
 15. A device comprising: a cover article, thecover article comprising a substrate comprising a substrate surface, andan optical film disposed on the substrate surface forming a coatedsurface, wherein the optical film comprises a scratch-resistant layerand an optical interference layer disposed between the scratch-resistantlayer and the substrate, the optical interference layer comprising atleast one set of sub-layers, the set of sub-layers comprising a firstlow refractive index (RI) sub-layer and a second high refractive index(RI) sub-layer, the scratch-resistant layer having a physical thicknessfrom 0.1 microns to 3 microns, the optical interference layer comprisesa physical thickness of about 800 nm, wherein each of the sub-layers inthe optical interference layer has an optical thickness (n*d) in therange from 2 nm to 200 nm, and at least one layer in the opticalinterference layer comprises an optical thickness of 50 nm or greater,wherein the cover article comprises a maximum hardness of 8 GPa orgreater, as measured by a Berkovich Indenter Hardness Test alongindentation depths of about 100 nm or greater, wherein the cover articlecomprises a color shift of less than 2, when viewed at an incidentillumination angle in the range from about 2 degrees to about 60 degreesfrom normal incidence under an illuminant comprising CIE A illuminants,CIE B illuminants CIE C illuminants, CIE D illuminants or CIE Filluminants, and further wherein the color shift is determined by theequation √((a*₂−a*₁)²+(b*₂−b*₁)²), where a*₁ and b*₁ are coordinates ofthe article when viewed at normal incidence and a*₂, and b*₂ arecoordinates of the article viewed at the incident illumination angle,and wherein the coordinates of the article when viewed at normalincidence and at the incident illumination angle are both intransmittance or reflectance.